JPH11312848A - Optical amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To divide an optical amplifier into modules, to execute maintenance and inspection and to search trouble easily, by modularizing the optical amplifier into optical amplifiers at a pre-stage and a post-stage, and connecting the modules by optical connectors, etc. SOLUTION: A light signal transmitted to an isolator 1 is inputted to a pre-stage optical amplifier as it is and amplified. Energy for amplifying the light signal is fed from laser diodes LD1, LD2, LD3. The light signal inputted to a compensation fiber to dispersion is compensated, and inputted to a post- stage optical amplifier again from a connector 2. The light signal is branched by a BS4, and received by a PD 4. Since gains are equalized respectively on both sides of pre- and post-stages, the pre- and post-stages are manufactured separately and can be combined afterwards. Since the uniform light signal can be delivered, an interface between the preand post-stages can be conducted easily. Since the constitution of an optical amplifier for wave-length multiplexing is complicated, a modularized optical amplification section and a DCM are configured detachably of an optical connector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wavelength-division multiplexing (WDM) of a plurality of optical signals having different wavelengths.
The present invention relates to a wavelength division multiplexing optical amplifier used in a wavelength division multiplexing optical communication system for transmitting signals via an optical fiber transmission line and suitable for amplifying a wavelength multiplexed optical signal.

[0002]

2. Description of the Related Art In order to construct a multimedia network in the future, an optical communication system having a larger capacity is required. The Internet, broadband ISDN (B-ISDN), etc. have become widespread, and several Mb / s
When households begin to handle this information, the transmission capacity of the trunk system becomes larger than the current communication capacity based on the telephone network (64 kb / s).
A terabit (Tb / s = 1,000 Gb / s) class that is two orders of magnitude larger will be required. For this reason, research institutes in Japan and abroad have adopted time-division multiplexing (TDM) and time-division multiplexing (OTDM: Optical Time-Division) M
ultiplexing), WDM (Wavelength-Di
Researches such as vision multiplexing are being actively conducted.

Among these, the WDM transmission system employs an erbium-doped optical fiber amplifier (EDFA: amplifying an optical signal at an optical level).
Utilizing the wide gain bandwidth of the Erbium-Doped Fiber Amplifier, cross-connect and drop / insert (Add / Dro
It is also expected as a means to realize a flexible, so-called lightwave network that performs p). With the progress of the research and development of such WDM transmission systems, research on the development of optical fiber amplifiers into wavelength division multiplexing optical fiber amplifiers based on EDFAs already in practical use has been actively conducted. Wavelength multiplexing optical fiber amplifiers, which are key components of wavelength multiplexing optical communication systems, are generally wavelength multiplexed using single-mode optical fibers doped with rare earth ions such as erbium ions (Er ³⁺ ). Refers to an optical fiber amplifier that amplifies optical signals of multiple wavelengths collectively. The most common erbium-doped optical fiber amplifier has a wide gain band of 4 THz or more at about 35 nm from 1530 nm to 1565 nm. In this gain band, signal lights having different wavelengths of several tens to one hundred wavelengths are wavelength-multiplexed and collectively amplified.

[0004]

In a wavelength division multiplexing optical communication system, a wavelength division multiplexing optical fiber amplifier, which is one of the key components, is used to collectively amplify a plurality of wavelength division multiplexed optical signals having different wavelengths. Has the following problems.

(1) Wideband characteristics for amplifying multi-wavelength signals, (2) Flatness of gain over a wide input dynamic range with respect to wavelength, (3) Controllability of optical output of each channel, (4) Dispersion compensator (5) Optical output control for fluctuations in the number of input channels.

The basic characteristics of an optical fiber amplifier include (6) low noise characteristics and (7) high output characteristics (or
High efficiency characteristics when the pump light power is converted to the signal light power).

Among them, the problem (2) is that the wavelength division multiplexing ED is used.
This is important when an FA is used as an optical amplification repeater (in-line amplifier). If there is a wide dynamic range, the same optical fiber amplifier can cope with the case where the loss in the relay section is different.

The problem (3) is that each wavelength-multiplexed channel (each wavelength) needs to be received at the receiving end while maintaining good quality. For this purpose, each channel of the optical amplification repeater is required. It is necessary to define upper and lower limits for the output of the channel. This is a problem that occurs because the optical amplification repeater does not have functions such as waveform shaping and timing extraction of the regenerative repeater, and noise is accumulated. The upper limit is the self-phase modulation (SPM:
lf-Phase Modulation), cross-phase modulation (XPM: Cross-Phas
e Modulation), Four-Wave Mixing (FWM)
The signal waveform is defined so as not to be degraded by the nonlinear effect. The lower limit is defined so as to suppress deterioration of the signal-to-noise ratio (SNR) due to noise light (ASE: Amplified Spontaneous Emission) generated from the optical fiber amplifier. In the output of the optical fiber amplifier, the optical output of each channel (each wavelength) needs to fall within this range.

The problem (4) is that the transmission path is 1.3 μm zero-dispersion single mode optical fiber (SMF).
In the case of r), if a signal with a wavelength of 1.55 μm existing in the amplification band of the EDFA has a dispersion of about 18 ps / nm / km on the transmission line, a signal with a high transmission rate such as 10 GHz is transmitted. This is due to the problem that the waveform is distorted. In order to solve this, for example, there is a method of compensating the transmitted signal by giving the transmitted signal a (negative) dispersion that is exactly the opposite of the dispersion generated in the relay section in each repeater. In this case, the insertion loss of the dispersion compensator is also compensated by the optical fiber amplifier.

The problem (5) becomes an important problem when the wavelength division multiplexing optical fiber amplifier is applied to a so-called lightwave network which performs cross-connect or add / drop at an optical level. That is, although the number of channels input to the optical fiber amplifier changes during operation, the output of each channel also needs to maintain a predetermined value.

An object of the present invention is to solve the above-mentioned problems, and in particular, to provide an optical amplifier most suitable for a wavelength division multiplexing transmission system. Another object of the present invention is to provide an optical amplifier capable of reducing manufacturing, maintenance and inspection costs of an optical amplifier which is complicated to solve the above-mentioned problem.

[0012]

According to the present invention, there is provided an optical fiber doped with a rare earth element,
A pre-stage optical amplifier having a pump light source for inputting pump light to the optical fiber, a second optical fiber doped with a rare earth element, and a post-stage having a pump light source for inputting pump light to the second optical fiber; An optical amplifier is provided, and the former optical amplifier and the latter optical amplifier are optically connected via a detachable optical coupling unit.

According to the second aspect of the present invention, there is provided an optical fiber doped with a rare earth element to which a plurality of wavelength-multiplexed optical signals having different wavelengths are inputted, and an optical fiber provided at an output side of the optical fiber. A pre-stage optical amplifier having gain equalizing means for compensating for the wavelength dependence of the gain characteristics of the gain characteristics, and a post-stage optical amplifier having a second optical fiber doped with a rare earth element, wherein the pre-stage optical amplifier and the post-stage The optical amplifying unit is achieved by optically connecting via a detachable optical coupling unit.

Further, according to the third aspect of the present invention, there is provided a pre-stage optical element having an optical fiber doped with a rare earth element to which a plurality of wavelength-multiplexed optical signals of different wavelengths are inputted, and outputting an amplified optical signal. An amplifier, a dispersion compensating unit that compensates for dispersion of each optical signal output from the pre-stage optical amplifier, and outputs the optical signal; and a rare earth element doped with a rare earth element to which each optical signal output from the dispersion compensating unit is input. Two optical fibers,
Gain equalizing means provided on the output side of the second optical fiber and compensating for the wavelength dependence of the gain characteristics of the second and third optical fibers; and each optical signal output from the gain equalizing means And a third-stage optical amplifier having a third optical fiber doped with an input rare earth element.

[0015]

FIG. 1 is a system configuration diagram of an optical wavelength division multiplexing transmission system. In the system shown in FIG. 1, the bit rate specified by the North American SONET transmission system is 10 Gb.
A different wavelength (channel) is assigned to each of the optical signal frame OC-192 of ps and the optical signal frame OC-48 of bit rate 2.4 Gbps, wavelength multiplexing is performed up to 32 channels, and one single mode optical fiber SMF
Is shown in FIG. Each optical signal is input from the left side (west side) in the figure and is input to the right side (E
AST), input from the right side (EAST side) of the figure, and transmitted to the left side (WEST) of the figure.

The 10 Gbps transmission apparatus W1 on the WEST side in FIG. 1 includes an optical signal transmitting unit OSW1 and an optical signal receiving unit OSW1.
RW1. The optical signal transmitting unit OSW1 converts the lightwave having the wavelength λ1 into one according to the SONET STS-192 frame.
A single-wavelength optical signal (10 Gbps) modulated by an electrical signal of 0 Gbps and having a wavelength λ1 according to the OC-192 optical signal frame.
s) is output. The optical signal having the wavelength λ1 is converted into an optical variable attenuator V provided on the input side of the next-stage wavelength division multiplexer WMUXA.
Output to ATA1. The optical signal receiving unit ORW1 transmits the OC-19 transmitted through the single mode optical fiber.
A single wavelength optical signal (10 Gbps) having a wavelength λ1 according to a two-optical signal frame is converted into a wavelength multiplexing / demultiplexing device WMUXA
And reproduces an electrical signal of 10 Gbps received from the optical wavelength demultiplexer RWDA on the output side according to the STS-192 frame. 10Gbp on the EAST side of FIG.
The s transmission device E1 has the same configuration as the 10 Gbps transmission device W on the WEST side, and includes an optical signal receiving unit ORE1 and an optical signal transmitting unit OSE1. Optical signal receiving unit ORE1
Is a single wavelength optical signal (10 Gb) of wavelength λ1 according to the OC-192 optical signal frame from the optical wavelength demultiplexer RWDB on the output side of the wavelength multiplexing / demultiplexing apparatus WMUXB in the preceding stage.
ps) and 10 according to the STS-192 frame.
A Gbps electric signal is reproduced. Optical signal transmission unit OSE1
Modulates a lightwave of wavelength λ1 with a 10 Gbps electrical signal according to SONET STS-192 frame,
A single-wavelength optical signal (10 Gbps) having a wavelength λ1 according to a -192 optical signal frame is transmitted to the next-stage wavelength division multiplexer WM.
Output to the variable optical attenuator VATB1 provided on the input side of UXB.

Note that the variable optical attenuators VATA, VATB
Need not be provided one-to-one with respect to the optical signal transmission units OSW and OSE, and it is also possible to attenuate the optical signals from a plurality of optical signal transmission units at once.

Similarly, 2.4G on the west side of FIG.
The bps transmission device Wn includes an optical signal transmitting unit OSWn and an optical signal receiving unit ORWn. The optical signal transmission unit OSWn modulates the lightwave having the wavelength λn with an electric signal of 2.4 Gbps according to the STS-48 frame of SONET, and modulates the OC-48.
A single-wavelength optical signal (2.4 Gbps) having a wavelength λn according to the optical signal frame is converted into a wavelength division multiplexer WMUX at the next stage.
Output to the variable optical attenuator VATAn provided on the input side of A. The optical signal receiving unit ORWn is a single wavelength optical signal (2.4 Gbp) having a wavelength λn according to the OC-48 optical signal frame transmitted via the single mode optical fiber SMF.
s) is received from the optical wavelength demultiplexer RWDA on the output side of the wavelength multiplexing / demultiplexing apparatus WMUXA in the preceding stage, and STS-4
A 2.4 Gbps electric signal according to eight frames is reproduced. The 2.4 Gbps transmission device E on the EAST side in FIG.
n has the same configuration as the 2.4 Gbps transmission device Wn on the WEST side, and includes an optical signal receiving unit OREn and an optical signal transmitting unit OSEn. The optical signal receiving section OREn receives a single-wavelength optical signal (2.4 Gbps) having the wavelength λn according to the OC-48 optical signal frame from the optical wavelength demultiplexer RWDB on the output side of the wavelength multiplexing / demultiplexing apparatus WMUXB at the preceding stage. , An electric signal of 2.4 Gbps according to the STS-48 frame is reproduced. The optical signal transmitting unit OSEn has a wavelength λ
n is modulated with a 2.4 Gbps electrical signal according to the SONET STS-48 frame, and a single-wavelength optical signal having a wavelength λn according to the OC-48 optical signal frame (2.4).
Gbps) is output to the variable optical attenuator VATBn provided on the input side of the next-stage wavelength division multiplexer WMUXB.

10 Gbps transmission apparatuses W1, E1 and 2.
The 4 Gbps transmission devices Wn and En are both optical transmission devices that constitute an existing SONET high-speed optical communication network. The optical wavelength multiplex transmission system of FIG. The wavelength division multiplexing / demultiplexing apparatus WMUXA receives up to 32 channels of the optical signals λ1 to n, performs wavelength multiplexing (multiplexing), and performs wavelength division multiplexing optical signal (WDM).
Signal). The wavelength multiplexed optical signal is input to one existing single mode optical fiber SMF. In order to compensate for the loss of the single mode optical fiber SMF, a wavelength division multiplexing optical fiber amplifier including an Er-doped optical fiber as an optical amplification fiber is used as an optical repeater, and these wavelength division multiplexed optical signals are collectively amplified. Then, the signal is transmitted to the opposing optical wavelength multiplexer WMUXB. Optical wavelength multiplexer W
The MUXB separates the received wavelength multiplexed signal into single wavelength optical signals λ1 to n for each channel (wavelength) (demultiplexing).
Then, the signal is transmitted to the EAST-side optical transmission devices E1 to En. In FIG. 1, only the 10 Gbps transmission device E1 and the 2.4 Gbps transmission device En are shown, but the wavelength multiplex transmission is a transmission method independent of the bit rate, and is 600 Mbps.
Other different transmission rates (bit rates) such as s transmission equipment (transmitting optical signals according to OC-12 optical signal frames)
It is also possible to assign a specific channel to the optical signal.

In order to perform wavelength division multiplexing transmission, the wavelengths used for optical transmission of each optical transmission device need to be different from each other. However, existing optical transmission devices do not always output optical signals of different wavelengths. Therefore, before inputting the optical signals to the wavelength multiplexing / demultiplexing devices WMUXA and WMUXB, the transponder (wavelength converter) uses a wavelength multiplexing transmission system. It is assumed that the wavelength is converted to a convenient wavelength.
Although the transponder is not shown in FIG. 1, it is assumed in FIG. 1 that the transponder is provided for each channel at the input end and the output end to the wavelength division multiplexers WMUXA and WMUXB. FIG.
In the figure, the input light wavelengths from the optical transmission devices W1 to Wn and E1 to En to the wavelength multiplexing / demultiplexing devices WMUXA and WMUXB are shown to be different wavelengths λ1 to λn for each existing system.

The wavelength multiplexing / demultiplexing devices WMUXA and WMU are converted from the existing single wavelength optical transmission devices W1 to Wn and E1 to En.
The optical signals of wavelengths λ1 to λn input to the XB are input to optical variable attenuators (VATA1 to n and VATB1 to n) provided for each optical signal of each wavelength (channel). The optical signal input from the existing optical transmission device to the variable optical attenuator VAT has a different optical power level because the environment in which the signal is transmitted differs for each optical signal. Accordingly, when an optical variable attenuator is provided for each channel to adjust the input level of each optical signal to the optical wavelength multiplexers TWMA and TWMB, and when each optical signal propagates through the wavelength division multiplexing transmission system, the wavelength (channel) Make sure that there is no level difference for each. The optical signal whose optical power level has been adjusted by the optical variable attenuator is input to an optical wavelength multiplexer (TWMA, TWMB).
It is wavelength-multiplexed and output as an optical wavelength multiplexed signal (WDM). Next, the optical wavelength multiplex signal is transmitted to an optical post-amplifier (TWA).
A, TWAB), amplified and output. An optical post-amplifier (TWAA, TWAB) is an optical amplifier for wavelength multiplexing, and includes an Er-doped fiber for optical amplification, and a pumping light source usually used for supplying energy for optical amplification to the Er-doped fiber. Having. Further, additional pump light source units BSTA and BSTB can be added in accordance with an increase in the number of channels (wavelengths). If the pumping light is supplied to the Er-doped fiber to amplify the input optical signal of each channel with a predetermined gain, it is necessary to increase the pumping light power in proportion to the number of channels. Therefore, if the pump light power that can be supplied by the pump light source that is normally used becomes insufficient due to the increase in the number of channels, and it becomes impossible to amplify with a predetermined gain, the additional pump light source units BSTA and BSTB are added and the pump light Increase power.

The optical wavelength multiplexed signal amplified by the optical post-amplifiers TWAA and TWAB is partly branched and input to an optical spectrum analyzer (SAUA, SAUB). The optical spectrum analyzers SAUA and SAUB detect the power level of the optical signal of each channel included in the amplified optical wavelength multiplexed signal, and determine whether the power level is an appropriate value. Then, the result of this determination is converted into optical variable attenuators VATA1 to VATA, VATB provided for each channel input.
1 to n, and the optical preamplifiers TWAA, TWA
The optical attenuation of each optical variable attenuator is adjusted so that the output of the WAB becomes appropriate, and the level of the optical signal for each channel is adjusted.

Optical wavelength division multiplexers WMUXA, WMUX
The management unit MCA unit and the HU shown inside B
BA is a monitoring device composed of an LSI or the like, and performs processing of a detection result of SAU1 and processing of an alarm signal and the like. Details will be described later.

Optical repeaters 1-3 are optical in-line amplifiers L
It includes WAW1 to LWAW3 and LWAE1 to LWAE3, and functions as a relay station for amplifying an optical wavelength multiplexed signal attenuated by propagating through a single mode optical fiber. Each of the optical repeaters 1-3 has an optical in-line amplifier LWAW1-
In addition to LWAW3 and LWAE1 to LWAE3, additional excitation light source units BSTW1 to BSTW3 and BSTE
1 to BSTE 2 are provided, and HUBs 1 to 3 and MC units 1 to 3 as these monitoring devices are built in. Although three optical repeaters are shown in the figure, the number of optical repeaters is not limited to three, but a required number should be provided according to the transmission distance.

The wavelength multiplexed light output from the optical repeater 3 or 1 is input to the optical preamplifier RWAB or RWAA provided in the wavelength multiplexing / demultiplexing device B or the wavelength multiplexing / demultiplexing device A, and is amplified. Optical preamplifiers RWAB and RW
AA is also a wavelength multiplexing optical amplifier like other optical post-amplifiers and optical in-line amplifiers, and includes an Er-doped fiber and a pump light source for supplying pump light power to the Er-doped fiber. The wavelength multiplexing / demultiplexing apparatuses B and A are provided with additional pumping light source units BSTB and BSTA, and are configured to be able to supply insufficient pumping light power to the optical preamplifiers RWAB and RWAA due to an increase in the number of channels. The optical preamplifiers RWAB and RWAA input the amplified optical wavelength multiplexed signal to the optical wavelength demultiplexers (RWDB and RWDA), and demultiplex (demultiplex) them into optical signals of each wavelength.
Each optical signal of each wavelength-separated channel is converted by a transponder into an existing optical transmission device 10G that is input thereafter.
It is converted into an optical wavelength that can be received by the bps transmission devices E1 and W1 and the 2.4 Gbps transmission devices En and Wn. In the figure, the 10 Gbps optical signal of the wavelength λ1 is transmitted to the optical signal receiving unit ORE1 of the optical transmission device E1 and the optical signal receiving unit O1 of the optical transmission device W1.
The 2.4 Gbps optical signal having the wavelength λn that is input to the RW1 is input to the optical signal receiving unit OREn of the optical transmission device En and the optical signal receiving unit ORWn of the optical transmission device Wn. That is, the optical signal input to the optical wavelength division multiplexing system from one (west side) 10 Gbps transmission apparatus W1 is transmitted to the other (EEST side).
The optical signal transmitted to the 10 Gbps transmission device E1 on the AST side) and the optical signal input from the 2.4 Gbps transmission device Wn on the WEST side to the optical wavelength division multiplexing system are transmitted to the other (EAS).
(T side) to the 2.4 Gbps transmission device En.

In FIG. 1, the 10 Gbps optical transmission device W1,
The E1 and 2.4 Gbps optical transmission devices Wn and En are of a key type, and the EAST side and the WEST side of the lower optical wavelength multiplexing system (b) (the same configuration as the upper optical wavelength multiplexing system (a)). Optical signal transmission units OSE respectively corresponding to
1 ′, OSEn ′ and OSW1 ′, OSWn ′ and optical signal receiving units ORE1 ′, OREn ′ and ORW1 ′, ORW
n ′ are provided. This is because the optical wavelength multiplexing systems (a) and (b) are designed to constitute a network having a loop (ring) topology, that is, a SONET ring network. Accordingly, in the lower optical wavelength multiplexing system (b), the left side is the EAST side and the right side is the WEST side in the figure, and the optical signal is transmitted in a loop. Note that the optical wavelength multiplexing system does not necessarily have to be formed in a loop, but can be applied to a linear network.

Next, in the optical wavelength division multiplexing transmission system shown in FIG.
A description will be given of a transmission frame handled by the us Optical Network (transmission network) transmission method. Figure 2 shows SONE
3 shows a frame format of a basic transmission frame STS-1 handled by T. The STS-1 has a 9 × 3 byte overhead 10 in which various maintenance operation (monitoring control) information such as a frame synchronization signal and a parity check signal are stored, and a 9 × 87 byte overhead in which actual communication data is stored. It has a total of 9 × 90 bytes of information with the payload 20, and in SONET, this 90 × 9 bytes (= 81
0 bytes) is transmitted 8000 times per second, so that 90 × 9 × 8 × 8000 = 51.84 Mbps
[TSS-1 (Synchron
ous Transport Signal Leave
l 1)] is configured. Note that the SONET transmission method is based on the international standard SDH (Syn) defined by ITU-T.
chronous Digital Hierarch
y), which is a North American synchronous multiplex transmission standard.
In the SDH transmission method, a frame corresponding to STS-1 is transmitted using STM-0 (Synchronous Transfer).
Module Level 0).

The above overhead 10 includes FIG.
As shown in (1), when communication is performed between the terminal station multiplex relay transmission device (LTE) and the add / drop multiplexer (ADM) or between the add / drop multiplexer (ADM), the content is terminated in the LTE and ADM and the content is terminated. When communicating between the section overhead (SOH11) to be replaced and LTE, each LT
A line overhead (LOH12), which is terminated at E and is replaced, is prepared. Note that S
In DH, section overhead is called relay section overhead (R-SOH), line overhead is called multiplexed section overhead (M-SOH), and R-SOH and M-SOH are collectively called section overhead (SOH). In some cases.

Various overhead management information is prepared in the overhead 10, and for example, as shown in FIG.
1, A2 byte and transmission error monitoring on the section 11A [BIP (Bit Interleaved Parity)
ty)] Byte B1, data communication channel (DCC) bytes D1 to D3 (192 kbps data link) for performing communication for monitoring and control in section 11A, and the like are defined. BIP byte B2 and APS (Automatic
Protection Switch) Bytes K1 and K
2. DCC bytes D4 to D12 on line 12A
(A data link of 576 kbps) and the like are defined. 2 and 4, the pointer byte [A
U (Administrative Unit) pointer] 13 stores a phase of a transmission frame and a management data unit (VT: Virtual) stored in payload 20.
This is for indicating the difference from the frame phase of the Tributary Unit by an address.
3, it is possible to establish VT frame synchronization at high speed.

In SONET, a basic transmission frame (STS-1) having such a frame structure is defined as n
By performing time division multiplexing (byte multiplexing) in units of frames (where n = 3, 12, 48, 192, etc.), an STS-n frame is configured as shown in FIG. For example, if STS-1 frames are byte-multiplexed for three frames, STS-3 (51.84 Mbps × 3)
= 155.52 Mbps), and if bytes are multiplexed for 12 frames, STS-12 (622.08 Mbps), 48
If bytes are multiplexed for frames, STS-48 (2.488)
Gbps), STS if byte multiplexing for 192 frames
A high-speed signal of -192 (9.953 Gbps) is formed. In SDH, STM-N (N = n / 3)
Correspond to signals having the same transmission speed as STS-n.

Here, the STS-1 described with reference to FIG.
For example, in the case of N.92 (OC-192 in the optical signal frame), the frame configuration is 9 × 57 as shown in FIG.
6 (3 × 192) bytes of overhead 10 and 9 × 1
6,704 (87 × 192) bytes of payload 20. However, not all bytes of the overhead 10 are byte-multiplexed. Special signals (A1, A2 byte, BIP byte B2, etc.) are n-byte multiplexed, and the other control signals are multiplexing numbers. Is constant regardless of For this reason, at present, overhead 1
Most of the 0s are unused areas.

In the optical wavelength division multiplexing system of FIG.
O which is an optical signal frame corresponding to TS-192 and TS-48
C-192, 48 (Optical Carrier-
Level 192, 48) are wavelength-multiplexed for a maximum of 32 channels and transmitted as a wavelength-multiplexed signal through one single-mode optical fiber.

In the optical wavelength division multiplexing system of FIG. 1, optical repeaters 1 to 3 comprising optical in-line amplifiers LWAW1 to LWAW3 and LWAE1 to E3 are connected to a single mode optical fiber transmission line SM.
It is provided in the middle of F. Optical post amplifier TWAA,
Including TWAB and optical preamplifiers RWAB, RWAA,
The optical amplifier used in the optical wavelength division multiplexing system of FIG. 1 is basically an amplification band (gain band) of an Er-doped fiber.
It has only the function of amplifying the optical signal inside. However, these optical repeaters 1 to 3 are often installed in unmanned stations at remote locations distant from the nodes W and E, and require a function of monitoring the optical repeaters 1 to 3 by some method. Also, the optical wavelength multiplexing system of FIG. 1 can wavelength multiplex an optical signal of a maximum of 32 wavelengths (channels) and transmit the multiplexed signal through one single mode optical fiber SMF.
At the time of system introduction, for example, it is practical to transmit only optical signals for four wavelengths (channels) and to add channels in accordance with an increase in traffic from the viewpoint of cost. It is desirable that the channel can be added while the operation of the system is continued. As described above, when the number of channels is increased, the pumping light power supplied to the Er-doped fiber may be insufficient.
, BSTEs 1-3 and BSTA, BSTB need to be added in stages, and a function of controlling the optical repeaters 1-3 in accordance with the addition of channels is required. Therefore, in the optical wavelength division multiplexing system of FIG.
Optical service channel OS for transmitting control signals
C is the gain band of the Erdof fiber (typically about 153
It is configured to transmit using an optical signal of an outside wavelength (in the range of optical wavelengths from 0 nm to about 1560 nm).

The wavelength division multiplexers WMUA and WMUXB
The optical service channel interface OSCI converts an optical wavelength multiplexed signal (including optical signals for up to 32 channels) amplified by the optical preamplifiers TWAA and TWAB into an optical service channel interface OSCI.
A, the optical signal for monitoring / control output from OSCIB is further wavelength-multiplexed and input to the single mode optical fiber SMF. In each of the optical repeaters 1 to 3, the optical in-line amplifier LW
The monitoring and control optical signals are demultiplexed by the inputs to AW1 to 3 and LWAE1 to 3 and input to the optical service channel interfaces OSCIW1 to 3 and OSCIE1 to 3 to be converted into electric signals and then monitored by HUB1 to 3・ Transfer control signals. The monitoring and control signals output from the HUBs 1 to 3 correspond to the optical service channel interface OSC.
The optical in-line amplifier LW is converted into an optical signal by the IW1 to 3 and OSCIE1 to 3 and is monitored and controlled as an optical signal.
The wavelengths are further multiplexed with the optical wavelength multiplexed signals amplified and output by the AWs 1 to 3 and the LWAEs 1 to 3. In the optical wavelength division multiplexing / demultiplexing devices WMUXB and WMUXA, the monitoring / control optical signal is demultiplexed at the input of the optical preamplifiers RWAB and RWAA, and the optical service channel interface OSCI
B, input to OSCIA and converted to electrical signals. HUBB, H of the optical wavelength division multiplexer WMUXB, WMUXA
In the UBA, monitoring and control of the optical repeaters 1 to 3 can be performed by analyzing the monitoring / control signal converted into the electric signal.

FIG. 7 is a table showing an example of the channel arrangement (wavelength) in the optical wavelength division multiplexing transmission system of FIG. I
In the TU-T recommendation draft Gmcs, as a wavelength (channel) arrangement in an optical wavelength division multiplexing transmission system using an Er-doped fiber, as shown in FIG.
The channels are arranged on a grid at an interval of 100 GHz (approximately 0.8 nm in terms of wavelength) with a reference wavelength of 52 nm. In the optical wavelength division multiplexing system shown in FIG. 1, in accordance with this recommendation draft, when four wavelength division multiplexing, eight wavelength division multiplexing, 16 wavelength division multiplexing and 32 wavelength division multiplexing are performed, each wavelength (channel) is indicated by a grid indicated by an X mark in FIG. Has been placed. Then, the optical service channel OSC is set to the optical wavelength 1510 outside the gain band (amplification band) of the Er-doped fiber.
nm. Of course, these channel arrangements are examples, but according to the channel arrangement of FIG.
Up to wavelength multiplexing, optical wavelength multiplex transmission can be performed using a half band of the gain band of the Er-doped fiber, and the gain band of the Er-doped fiber (1530 nm to 1
560 nm), compared with the case of using all of them, the broadband characteristic required for the optical amplifier including the Er-doped fiber is relaxed.

Next, the transmission format of the optical service channel OSC will be described. In the optical wavelength division multiplexing transmission system of FIG. 1, a DS1 format of 1.544 Mbps is used as a transmission format for OSC. FIG.
Indicates an OSC transmission format. As shown in FIG. 11, in the OSC transmission format, 1 to 24 subframes Sub constitute one frame. Between each sub-frame, 1-bit frame synchronization bits F1 to F24 are arranged. By detecting a specific bit pattern composed of these F1 to F24, frame synchronization is performed and the first bit of one frame is determined. Identify. One sub-frame Sub is composed of 24 time slots (8 bits).
Is inserted. Further, the byte information of the time slot 23 has a multi-frame structure, and as shown in FIG.
Each multi-frame is constituted by 8 × 24 bits (24 bytes) of byte information of each time slot 23. In this one multi-frame, the contents of bytes 1 to 8 are:
It is as shown below. 1) Bytes 1 to 4 (32 bits) WCRs 1 to 4: Wavelength Channel
Rate The transmission rate (10 Gbps or 2.4 Gbps) of each channel (wavelength) is indicated by 1 bit. 2) Bytes 5-8 (32 bits) WCS 1-4: Wavelength Channel
Status Each channel (wavelength) is in operation (In-Service)
It is indicated by one bit indicating whether the data is empty or out-of-service. 3) Bytes 9 to 24 Reserve (reserved bytes) Of these byte information, time slots 9 to 10, 1
Reference numerals 3 to 16 and 19 to 24 include control information necessary for controlling the optical amplifier (particularly, control associated with channel addition / removal), and are provided in the wavelength division multiplexers WMUXA, WMUXB, and the optical repeaters 1 to 3. OSC interface OSC
IA, OSCIB, and OSCIW1 to OSCIW3 are terminated. Other byte information is terminated in the MC unit and analyzed. Information terminated by the OSC interface will be described later.

Note that each byte information of OSC is represented by CMI (Co
(ded Mark Inversion) encoded and transmitted. Follow
Therefore, the clock speed of the DS1 frame in FIG.
It becomes 4 × 2 Mbps. FIG. 8 shows the optical transmission in FIG.
The detailed configuration of the device W1 and the wavelength division multiplexer WMUXA is shown.
FIG. The figure shows the optical wavelength division multiplexing transmission system of FIG.
(A) Upper row (from WEST to EAST) and lower row (EA
FIG. 9 is a diagram showing an integrated configuration of ST to WEST).
And one shelf. Light of optical transmission device W1
The signal transmitting unit OSW1 includes a narrow-band optical transmitter 1-1.
I have. The narrow-band optical transmitter 1-1 is provided from the semiconductor laser LD.
Light source and the DC light output from the semiconductor laser LD.
Amplitude with STS-192 signal of bit rate 10Gbps
And an external light modulator Mod for modulation. Outside
As the optical modulator Mod, LiNbO _ThreeMatrix using crystals
A Zach-Zehnder type optical modulator can be used. External light
The optical signal (corresponding to OC-192) output from the modulator is
This is an optical signal having a narrow spectrum width. Input from OSW1
Optical signals are provided for each input optical signal.
Data module (VATA1). VATA
At 1, a part of the optical signal is branched by the optical coupler 2-5.
Then, the light is received by the monitor 2-2. Monitor 2-2 is a node
Output from optical signal transmission unit OSW1 of optical transmission device W1 of W1
The presence or absence of the OC-192 signal is monitored. this is,
It is converted to an electrical signal and
Input to the source OSCIA.

On the other hand, the optical signal input to the variable optical attenuator (VATA1) 2-1 without being branched by the optical coupler 2-5 has its output optical power level adjusted, and is sent to the optical multiplexer 3-1 of the optical multiplexer module TWMA. Is entered. Then, it is input to the optical multiplexer module TWMA for wavelength multiplexing with optical signals having different wavelengths input from the variable optical attenuator modules VATA2 to VATAn provided for the other channels. The optical multiplexer module TWMA inputs an optical wavelength multiplex signal to the optical post-amplifier module TWAA. The wavelength multiplexed optical signal input to the optical post-amplifier module TWAA is amplified by the pre-stage optical amplifier 4-4 controlled by the CPU 4-1 and input to the dispersion compensating fiber DCF of the dispersion compensating fiber module DCMT11.
The dispersion compensating fiber is a single mode optical fiber S between the optical preamplifier TWAA and the optical in-line amplifier LWAW1.
It has an appropriate dispersion value for compensating for the dispersion added to the optical signal of each channel of the optical wavelength multiplexing signal by propagating through the MF, and gives this dispersion value to the optical signal of each channel.
The optical wavelength multiplexed signal in which an appropriate dispersion value is given to the optical signal of each channel is amplified again by the post-stage optical amplifier 4-5 and input to the optical coupler 4-6. A part of the optical wavelength multiplexed signal branched by the optical coupler 4-6 is converted to a spectrum analyzer 5-2 of the optical spectrum analyzer unit SAUA5.
The wavelength shift and power level of the optical signal of each wavelength (channel) included in the optical wavelength multiplex signal amplified by the optical preamplifier TWAA are measured. Then, the result is input to the CPU 5-1. The CPU 5-1 includes:
The result of the spectrum measurement of the optical wavelength multiplexed signal obtained by the spectrum analyzer 5-2 is processed, and the C
The result is notified to PU2-3. The CPU 2-3 determines a variable attenuator (VATA1) 2-1 based on the measurement result.
And the power level of the optical signal of the wavelength λ1 is controlled. For example, the wavelength of the optical signal of each channel is a predetermined value (for example, 0.05 n) from the grid shown in FIG.
m) If a wavelength shift of not less than m) is detected, it is determined that an error has occurred, the attenuation of the variable optical attenuator (VATA1) 2-1 is increased, and the optical signal of the channel in which the wavelength shift is detected is apparently changed. Set to signal cutoff state to prevent transmission of optical signals.

On the other hand, the OSC interface OSCIA
The monitoring control signal received by the monitor 2-4 from the monitor 2-2 is notified to the OSC interface OSCIA 4-3 of the optical post-amplifier module TWAA. OSCIA4-3
Detects the presence or absence of a failure from the received supervisory control signal. For example, when the occurrence of the signal interruption is notified, the attenuation of the variable attenuator (VATA1) 2-1 is maximized so that the optical signal is not input to the optical multiplexer TWMA.
On the other hand, from the OSC interface OSCIA2-4,
The OSCIA 4-3, which has received the monitoring control signal, sends the signal to the electrical / optical converter EO4-2, and converts it into a monitoring control optical signal having a wavelength of 1510 nm. The WDM coupler 4-7 multiplexes this monitoring control optical signal with the amplified optical wavelength multiplexed signal output from the optical preamplifier TWAA and transmits the multiplexed optical signal.

In the monitoring control signal (OSC) received by the OSCIA 4-3, the non-terminated time slots 1 to
Information of 7, 11, 12, 17, 18 (information communicated by a system operator such as an order wire signal OW and a data communication channel DCC) is stored in a hub unit (HU
BA) 8 overhead serial interface OH
The process is sent to S8-3, where the alarm is detected by the alarm detection unit ALM8-5 and processed with the HUB 8-2. Here, OSCIA2-4, 4 of each module
-3 and OSCIB 6-3, 7-2 and HUB 8-2, for example, communication is performed using ATM cells.
-3, communication between the OSCIB 6-3 and the OHS 8-3 is performed by serial data. OSCIA2-4, 4-
3 and the OSCIBs 6-3 and 7-2 receive the ATM cells for monitoring and control from the HUB 8-2, and
Is analyzed, and each unit is controlled according to the contents. It also receives monitoring and control signals from each unit and receives ATM signals.
The cells are converted to cells and output to HUB 8-2. HUB8-2,
Also, termination of each OSCI is performed. That is, each OSCI
The ATM cells sent from the ATM are matched. That is, the VCI of the transmitted ATM cell is analyzed, and the output to the OHS 8-3 and the output to each OSCI are selected and output according to the contents. Also, it interfaces with the monitor MON8-4 that monitors and controls its own unit. Alarm A
The LM 8-5 monitors information such as the end of alarm information from each unit and an error in an interface signal with the management device MCA unit. Monitor MON8-4 is HU
Information is extracted from the ATM cell based on the control information from the MCA unit output from B8-2, and control is performed. Also, alarm information detected in the unit is converted into an ATM cell and output to the HUB 8-2.

From the HUB 8-2, each information is transmitted via the optical / electrical converter 8-1 to an OC-3 signal (1) which is an optical signal.
Management device Management using 50Mbps)
It is transmitted to the Complex (MCA unit). M
In the CA unit, an optical / electrical converter (EO, OE) 9-
3, signals are exchanged, and the personal computer interface PCI 9-1 separates the monitoring control information from the overhead information. Overhead information is OH-MT
The data is sent to the RX 9-2, where overhead processing is performed.
The monitoring control information is sent to a personal computer as a console terminal and terminated. The MCA unit is provided in common for a plurality of shelves, and can control, for example, up to six shelves.

On the receiving side of the wavelength division multiplexing / demultiplexing device WMUXA, when a wavelength multiplexed optical signal is received from the single mode optical fiber SMF from the optical repeater station 1, it is monitored by the WDM coupler 6-6 of the optical preamplifier module (RWAA) 6. The control optical signal (wavelength 1510 nm) is demultiplexed and converted into an optical / electrical
OSC interface OSC
Terminate at IB6-3. In addition, OSCIB6-3 uses O
The overhead information is acquired from the HS8-3, and the
By communicating with -2, the front optical amplifier 6-4 and the rear optical amplifier 6-5 are controlled via the CPU 6-1 based on the monitoring control information and the overhead information. A dispersion compensation module DCMR for dispersion compensation is provided between the upstream optical amplifier 6-4 and the downstream optical amplifier 6-5, and the wavelength multiplexed optical signal received in the dispersion compensating fiber DCF propagates. Is configured to compensate for the dispersion added to the optical signal of each channel by transmitting a single mode optical fiber between the optical repeater 1 and the wavelength division multiplexer WMUXA.

The wavelength multiplexed optical signal amplified by the optical preamplifier RWAA is converted to an optical demultiplexer module RW
The optical signal is separated (demultiplexed) into optical signals of respective wavelengths by the optical demultiplexer 7-1 of the DA, and the optical signal is received by a PIN photodiode (PINPD) 10-1 which is a light receiver of the optical signal receiver (ORW1) 10 of the optical transmission device W1. The light is received and photoelectrically converted to a 10 Gbps STS-192 signal.

FIG. 9 is a diagram showing a configuration of the optical repeater 1. As shown in FIG. The wavelength-division multiplexed optical signal from the single mode optical fiber SMF is input to one of the OPT-IN1 to OPT-IN4 to the shelf of the relay station shown in FIG. To enter. First, the supervisory control optical signal is separated (demultiplexed) by the WDM coupler 31-7, converted into an electric signal by the optical / electrical converter 31-3, and converted into an OSC interface (OSCIW).
1) Input to 31-6. The OSCIW1 includes, as described above, the time slots 8 to 10 and 13 to 1 including control information necessary for controlling the optical amplifier in the monitoring control signal.
6, 19 to 24, and other information to OHS32-
Send to 3. The terminated information is HUB32-2.
Send to The operations of the HUB1 module and the management device MC are the same as those in FIG.

OSCIW1 receiving the monitor control signal
In (31-6), information is processed by communication with the HUB2 unit 32, and a control signal is output to the CPU 31-5 based on the result, and the preamplifier 3
1-1, the amplification factor of the latter-stage amplifier 31-2 is controlled.
The wavelength-division multiplexed optical signal that has not been split by the WDM coupler 31-7 is supplied to a pre-stage optical amplifier 31-controlled by the CPU 31-5.
1 and undergoes dispersion compensation by the dispersion compensation module DCM, and is again amplified by the latter-stage optical amplifier 31-2 controlled by the CPU 31-5. Then, the WDM coupler 31
At -8, the signal is multiplexed with the monitoring control signal converted to the optical signal by the electric / optical converter 31-4, and is output from OPT-OUT1 to OPT-OUT4.

The optical repeater station of FIG. 9 has one optical in-line amplifier module (LWA) 31 mounted as one shelf, and it is shown that four of these can be mounted. In this way, by housing the optical components in one shelf, an easy-to-handle optical device can be assembled.

FIG. 10 is a diagram showing a configuration of a transponder, not shown in FIG. 1, used for converting the wavelength of an optical signal. An OC-48 optical signal is input from the input side of the transponder. This optical signal is input to a 2.4 Gbps optical / electrical converter (O / E) 41-1 of the photoelectric conversion module 41. The optical / electrical converter 41-1 outputs 2.4 Gbps data and 2.
A 4 Gbps clock is output. At the same time, information such as the overhead information described with reference to FIG.
Is sent to In addition, the photoelectric conversion module 41
On the other side of the board for future upgrade, and input to the OHS 42-3.

As described above, the OHS 42-3 exchanges overhead information, and the HUB 42-2 terminates the signal from the OHS 41-3. HUB4
From 2-2, information is sent as an optical signal to the HED module 43 of the MC unit via the optical / electrical converter 42-1 and is converted into an electric signal by the optical / electrical converter 43-3. The information converted into the electric signal is PCI 43-1.
The overhead information and the supervisory control information are separated by O
The overhead is processed in the H-MTRX 43-2. Other control information is processed by a personal computer PC as a console terminal.

The OHS 41-3 includes an electric / optical converter 41-.
2 to generate and output a 2.4 Gbps optical signal OC-48. At this time, the wavelength of the optical signal (OC-48) is converted into the wavelength of the channel allocated by the wavelength division multiplexing system.

In the figure, the shelf of the photoelectric conversion module 41 is described so that 1 to 16 shelves can be mounted.
Overhead information and monitoring control information are collected from the OHS 41-2 of each shelf to the HUB module 42 and processed. As described above, the transponders are configured as shelves and they are housed in one rack, so that it is only necessary to connect the optical wiring and the electric wiring between these shelves. A good optical device can be manufactured.

FIG. 14 is a block diagram of the OWA provided in the RWAA of FIG.
FIG. 3 is a diagram showing a partial configuration of SCIB6-3. The supervisory control signal input to the O / E module 6-2 is converted from an optical signal to an electric signal, and the converted data and a clock signal generated based on the optical signal are input to the CMI decoder 52, respectively. Then, the data is transmitted to the CMI decoder 5.
2 and is input to the frame synchronization unit 53.
At this time, the clock signal is also transmitted to the frame synchronization unit 5 at the same time.
3 is input. The frame synchronization unit 53 detects a data frame of the monitoring control signal. The detection result is input to the protection unit 55, which measures the coincidence of the timings at which the frames occur, and when a predetermined number of coincidences are obtained, transmits a signal indicating that the frames are synchronized to the frame synchronization unit. On the other hand, the PG 54 extracts a clock from the signal before the CMI decoding, receives a timing at which a frame is generated from the protection unit 55, and provides a clock for establishing synchronization. The generated clock is supplied to the frame synchronization unit 53
And is used for frame detection by the frame synchronization unit 53. When the frame is synchronized, the data subjected to the frame synchronization processing together with the clock signal is input to the demultiplexer 58, and the monitoring control signal (WC
F; Wavelength Channel Failure, WCR; Wavele
ngth Channel Rate, WCS; Wavelength Channe
l State) is extracted. The BIP operation unit 56 acquires the parity from the output from the frame synchronization unit 53 and sends it to the comparator 57. The comparator 57 compares the monitor control signal output from the demultiplexer 58 with a parity bit,
When a parity match is obtained, each monitoring control signal is output as it is without holding it in the holding unit 59. The monitoring control signal output from the holding unit 59 is directly sent to the HUBA module 8 in FIG. 8 and is input to the selector 61 via the three-stage protection unit 60. The selector 61 is also supplied with a monitoring control signal (shown as provision) such as WCR or WCS input from an operator. These are sent from software operated by the operator. The selector 61 selects one of the received monitoring control signal and the monitoring control signal input from the operator in response to the input of an override signal also input from the operator via predetermined software, and selects the TWAA. Is output to the local CPU 4-1 which controls.

If an error has occurred in the parity check stage of the comparator 57, each of the monitoring control signals WCF, WCR, and WCS in the previous state is held in the holding unit 59 so as not to be output. . Then, it waits until the error is resolved, and when the error is resolved, the holding unit 59 sends WCF, WCR, and WCS to the HUBA module.

FIG. 15 is a block diagram of the OWA provided in the TWAA of FIG.
It is a figure showing a partial configuration of SCIA4-3. The OSC interface OSCIA4-3 of the TWA module is
WCF, W from OSCIA2-4 of ATA module
The monitoring control signal of CR and WCS is received. On the other hand, WCR and WCS are received as input from the operator.
The WCFs 1 to 32 are signals generated by the hardware by monitoring the state of the own device, and are input to the multiplexer 72 and also to the check processing unit 71. The check processing unit 71 checks what kind of signal is being sent, and also monitors each signal and performs a parity check and the like. The multiplexer is controlled in accordance with the contents of the check to multiplex and output the WCFs 1 to 32. Further, the WCR and WCS are input to the provision unit 73 from the 19 Mbps ATM interface. Here, it is determined whether or not the input of the operator is switched to the input from the VAT module. Similarly,
The mode setting is also performed on the WCF, and it is set whether the WCF sent from the OSCIA 2-4 of the VAT module is input to the multiplexer 76 or the input from the operator is input to the multiplexer 76.

In any case, the multiplexer 76 receives a monitoring control signal from the OSCIA 2-4 of the VAT or a monitoring control signal from the operator. The condition unit 74 controls each monitor control signal (WCF, WCR, WC
As S), what kind of signal is being input is monitored.

The multiplexer 76 outputs the signals WCF and W
The monitor control signals of CR and WCS are multiplexed and input to the frame generator 79. The BIP operation unit 75 reads the parity from the signal output from the multiplexer 76 and feeds it back to the input of the multiplexer 76 to set the parity bit.

The clock from the PG 78 is input to the frame generator 79. This clock converts the periodic wave output from the 49 MHz oscillator (XO) 82 into a digital P
The phase is controlled by LL77 and processed into a clock signal by PG78. The frame generator 79 inputs the clock signal from the PG 78 to the multiplexer 76, and the multiplexer 76 multiplexes the signal based on the clock signal. The data frame generated by the frame generation unit 79 is input to the CMI encoding unit 80 together with a clock signal, and after being encoded into a CMI code, is also input to the E / O module 81 together with the clock signal, and The signal is converted into an optical signal, and is combined with the main signal amplified by the optical amplifier as a monitoring control signal.

FIG. 16 shows the OSC interface OSCIW13 included in the LWAW1 module of the relay station shown in FIG.
FIG. 6 is a diagram showing a partial configuration of 1-6. OSCIW1 in FIG.
31-6 is the output of OSCIA2-4 in FIG.
And the input of OSCIB6-3. That is, the monitoring control signal separated by the coupler is O
/ E module 91 and is converted into an electric signal. The monitoring control signal converted into the electric signal is input to the CMI decoder 92 together with the clock signal and subjected to CMI decoding, and is also input to the frame synchronization unit 94 together with the clock signal. As described above, the protection unit 95
The PG 93 reads the clock signal from the electric signal before the CMI decoding and determines whether or not the frame synchronization has been obtained a predetermined number of times. The establishment clock is input to the frame synchronization unit 94.

The monitor control signal of the electric signal synchronized with the frame is input to the demultiplexer 97 together with the clock signal generated by the PG 93, and each monitor control signal (W
CF, WCR, WCS, etc.). The parity bit is input to the comparison unit 98, and is compared with the parity read from the frame-synchronized electric signal by the BIP operation unit 96. If there is a parity match, each demultiplexed monitoring control signal passes through the holding unit 99 as it is and is input to the multiplexer 104. If the parities do not match, each monitoring control signal is held in the holding unit 99 until the parity matches.

Each monitoring control signal output from the holding unit 99 is sent to the three-stage protection unit 100, and after being subjected to the three-stage protection, is input to the selector 102. From the operator,
A command is input to the provision unit 101 via a 19 Mbps ATM interface, and WCR or W
CS is input to selector 102. And also,
According to the override signal input from the operator, either the monitoring control signal received by the local CPU or the monitoring control signal input by the operator is transmitted.

The provision unit 101 sets the mode of sending each received monitoring control signal to the output side, or sending each monitoring control signal to the output side by input from the operator. According to this mode setting, either the received supervisory control signal or the supervisory control signal from the operator is input to the multiplexer 104 and multiplexed.
The WCF signal is a parameter that cannot be set by the operator, and the mode is not switched. The BIP operation unit 103 reads the parity from the signal output from the multiplexer 104, feeds it back as a parity bit to the input side of the multiplexer 104, and sets the parity bit.

The frame generation unit 105 includes an oscillator 109
Is digitally controlled in phase (DPLL 107), and a signal (PG 106) configured as a clock signal is input and used for frame generation. Further, as described above, this clock signal is also input to the multiplexer 104 to provide timing for signal multiplexing. The monitor control signal assembled into the frame is encoded together with the clock signal by the CMI encoding unit 108, and the EMI is generated based on the similarly input clock signal.
The electric signal is converted into an optical signal by the / O module 110, multiplexed with the main signal amplified by the optical amplifier, and output to the transmission line.

FIG. 17 shows RWAA, T of FIGS.
FIG. 3 is a diagram illustrating an interface between an OSC interface OSCIB, OSCIA, and OSCIW1 provided in WAA and LWAW1 and an overhead serial interface OHS.

As shown in FIG. 9A, the OHS LSI of the HUB module and the TWAA, RWAA and LW
Communication with the OSC LSI of the OSC interface such as the AW1 is performed by a serial data cable of 19 Mbps. Two cables are provided for bidirectional communication.

FIG. 9B is a diagram showing a format of data transmitted from the OHS to the OSCI. The first bit of the data is a start bit, and by detecting this, it is possible to recognize that the data has arrived.
This is followed by data. The data has 32 bytes,
The parity is calculated during the reception of the data, and is compared with a parity bit added at the end of the data to determine whether the data is normally received. In the figure, the parity is "odd". After the parity bit, a stop bit is provided to indicate the end of data.

FIG. 9C shows the format of data transmitted from OSCI to OHS. In this case, the data format is basically the same as that shown in FIG. 3B, starting with a start bit, continuing with a 32-byte data area and a parity bit, and finally ending the data with a stop bit. Again, the parity is detected during the reception of the data area, and the parity is finally compared with the value indicated by the parity bit.If they match, it is determined that the data has been normally received. to decide.

FIG. 18 is a diagram showing a signal-to-noise relationship in an optical wavelength division multiplexing transmission system using an optical wavelength division multiplexing amplifier. Although FIG. 1 illustrates a system that configures a linear communication path, the same applies to a loop system.

The optical wavelength division multiplexing transmission system shown in FIG. 1 includes an optical post-amplifier TWAA, a single-mode optical fiber transmission line SMF for transmitting an optical signal, an optical preamplifier RWAB, and an optical in-line amplifier LWAW1 provided on the transmission line SMF.
To 3, and the supervisory control optical signal processing units OSCIA, OSCIW1, and OSCIW transmitted by the optical service channel.
2, OSCIW3 and OSCIB. The lower part of the figure shows the change from the distance from the optical post-amplifier TWAA, the power of the propagated optical signal, and the noise added by the optical amplifier (such as ASE noise). The optical signal amplified by the optical post-amplifier TWAA is transmitted to the transmission line SMFA.
When the light is transmitted to the optical in-line amplifier LWAW1, the power becomes weak. Then, the reduced optical power is amplified and transmitted by the optical in-line amplifier LWAW1, and similarly attenuated in the transmission line SMFW1. This is repeated until the optical signal is received by the optical signal receiving unit while the optical signal is propagated through the transmission line SMF, converted into an electric signal, and the signal is reproduced.
The process of amplifying and transmitting the optical signal reduced by the loss of the MF by the optical amplifier is repeated. When an optical signal is amplified by an optical amplifier having an Er-doped fiber, noise, particularly ASE (Amplified Spontaneous), is used.
Emission) noise is added to the optical signal. The noise is also attenuated while propagating through the transmission line SMF, but this noise is amplified by the optical amplifier together with the optical signal.

As the transmission path SMF, generally, those of various manufacturers and those of the production year are used.
The loss characteristics of the MF are not uniform. That is, the optical amplifiers LWAW1 to 3 and RWAB are changed due to the difference in the distance between the optical amplifiers (the length of the SMF), the optical fiber SMF having poor transparency, or the repair at the time of cutting the optical fiber SMF.
It is necessary to absorb various optical input power differences and amplify and output an optical signal to a certain output.

In a WDM optical communication system, optical signals (main signals) of a plurality of channels are wavelength-division multiplexed and transmitted, and a supervisory control signal (SV signal; Supervisory signal) is similarly wavelength-multiplexed and transmitted. In the optical in-line amplifiers LWAW1 to 3 and the optical preamplifier RWAB,
The main signal is amplified, the SV signal is demultiplexed separately and S
The signal is separately processed by V signal processing units OSCIW1 to WCI3, wavelength-multiplexed again to the main signal, and transmitted.

FIGS. 19 and 20 show a wavelength division multiplexing optical amplifier (TWAA, TWAA,
FIG. As shown in FIG. 1, the optical amplifier of FIG. 1 is a system in which different wavelengths of up to 32 channels are multiplexed and transmitted, and carries the main signals (OC-48, OC-192).
In addition to the optical signal of the wavelength, a supervisory control signal (SV signal; supervisory signal) for monitoring and controlling the system has a wavelength (optical service channel; out of the gain band of the Er-doped fiber) different from the 32-wavelength optical signal. Wavelength; 1510
nm) and transmitted.

When the wavelength multiplexed signal is input to the optical in-line amplifier, first, only the SV signal is extracted by the WDM1 coupler. The extracted SV signal is further input to the WDM2 coupler, and the SV signal is extracted again. Thus, passing the SV signal through the two WDM couplers is as follows.
By simply passing through one WDM coupler, the wavelength separation is not complete, and a part of the optical signal having the wavelength of the main signal appears. It is intended to completely filter the wavelength component of the main signal to increase the SN ratio (signal-to-noise ratio) of the SV signal and receive the signal. The separated SV signal is output outside the main signal optical in-line amplifier shown in FIG.
It is processed by a V signal processing unit (OSCI). Then, as described later, the signal is multiplexed with the main signal again and the transmission path SM
Output to F.

The optical signal from which the SV signal has been removed by the WDM 1 is input to the beam splitter (BS) 1. This BS
1, the power of the main signal as a whole is split, for example, into a 10: 1 ratio.
Of the optical signals branched into 0: 1, 10/11 is output for transmission.

Of the 10: 1 branched optical signal at BS1, 1/11 is input to WDM3 for optical input monitoring, wavelength components other than the main signal are removed, and received by photodiode (PD) 1. Is done. The signal level of the main signal received by the PD 1 is AGC / APC (Automatic
Gain control / automatic power control) is input as a power level on the input side to the amplification medium EDF1 (Er-doped fiber).

The optical signal sent to the isolator 1 is directly input to and amplified by the EDF 1 which is the first (previous) optical amplifier. Energy (excitation light power) for amplifying an optical signal is supplied from a laser diode LD1 having an output wavelength of 980 nm and laser diodes LD2 and LD3 each having an output wavelength of 1460 nm. If the required value is obtained with one output power of LD, LD2 and LD3 may of course be one, and L
If the required power of the pre-stage optical amplifier can be obtained only with D1, LD
Only one may be used. Pump light from LD1 is input to EDF1 by a WDM coupler. Here, the fact that the WDM coupler is described as 0.98 WDM means that the pump light (980 nm or 0.98 μm) to be multiplexed has almost no power level loss and is multiplexed. If the pump light to be sent to the EDF suffers a large loss when multiplexed by the WDM coupler, much of the output of the LD 1 will be wasted.
A DM coupler is used.

LD1 has an output wavelength of 980 nm and E1
The energy level of the doped Er ions is excited using the absorption band of DF (erbium-doped fiber) of 980 nm, and the input wavelength-division multiplexed light is amplified based on the stimulated emission action. Since the operating bandwidth (wavelength width) of the 980 nm amplification band of the EDF is narrow, it is preferable to stabilize the oscillation wavelength of the LD 1, and it is conceivable to extract the 980 nm excitation light accurately using an optical filter or the like. On the other hand, the pump lights of the LD2 and LD3 are polarized in the vertical direction and the horizontal direction, respectively, and are polarized and combined by the polarization beam splitter (PBS) connected to the EDF1. Can be synthesized. Furthermore, the polarization-combined pump light is converted to EDF by a WDM coupler.
Sent to The transmission path for sending the pump light from LD2 and LD3 to the PBS includes laser diodes LD2 and LD3.
This is a polarization preserving fiber for preserving the polarization of the pump light (laser light) output from the optical disc, such as a so-called PANDA fiber. Thus, the pump light of LD1 is used for forward pumping, and the pump light of LD2 and LD3 is used for backward pumping. Therefore, although the pump light of LD1 travels in the same direction as the propagation direction of the main signal, LD2, L
The pump light of D3 travels toward the input side of the optical in-line amplifier in the direction opposite to the propagation direction of the main signal. ISO1 is
It is provided to prevent the pump lights of the LDs 2 and 3 from flowing backward. However, the pump light of LD2 and LD3 cannot be completely blocked. Therefore, there is a possibility that this pump light will be received by the PD 1 as it is. If this occurs, the actual input power level of the main signal cannot be detected, causing a problem in AGC / APC control.
The wavelength multiplexed light for input monitoring of / 11 further includes a long wavelength pass filter (LWPF).
er). This prevents the backflow of the pump light from the LDs 2 and 3 so that the PD 1 can receive only the main signal (wavelength multiplexed light).

In order to provide the EDF 1 with energy for amplification, the LDs 1 and 14 having an oscillation wavelength of 980 nm are used.
LD2 and LD3 having an oscillation wavelength of 60 nm are used. This is done to provide sufficient amplification energy to the EDF. That is, as an example, a single LD cannot provide sufficient pump light power, so a plurality of (laser diode) LDs are used. The LD1 is used for forward excitation, and contributes to amplification of the attenuated main signal when the main signal first enters the EDF. When the main signal is input to the EDF of the EDF1, the main signal propagates through the long-distance optical transmission line SMF, so that the optical power is small. When such an optical signal is amplified by the EDF, generation of noise is inevitable. However, in the 980 nm band of the EDF, generation of noise at the time of amplification is suppressed to a small level (about 3 dB close to the theoretical limit is achieved). Therefore, when amplifying the attenuated main signal, the main signal can be prevented from being buried in noise. However, in the 980 nm band, the efficiency of converting pump light energy to main signal energy is 146.
Since it is slightly lower than the 0 nm band, when amplifying the optical signal, the signal is first amplified in the 980 nm band,
Amplification is performed in a 1460 nm band such as 2 or LD3. That is, the pumping method of the LD2 and LD3 is backward pumping, and the optical signal propagating through the EDF is pump light of the LD1 and is amplified to some extent without deteriorating the SN.
It is amplified by the pump light of D2 and LD3. The amplification characteristic of the EDF in the 1460 nm band, which is the oscillation wavelength of the LD 2 and LD 3, is slightly large in noise. However, the efficiency of converting the power of the pump light into the power of the main signal is good, and a large output main signal can be obtained. I can do it. 980
If the power of the pump light required for the pre-stage optical amplifier can be obtained by one nmLD (LD1), LD2 alone and LD2 and LD3 are not necessary.

FIG. 21 is a table summarizing the characteristics of the excitation band of the EDF. As shown in the figure, the EDF has two bands that have been put into practical use, and one is at 980 nm.
The other band is the 1480 band (1460 nm; 1450 to 1470 nm is used for the preamplifier). 980 nm band excitation band (EDF absorption band)
Has a width of approximately 970 to 985 nm of 15 nm. The NF (noise figure) of the amplifier is low noise and the theoretical limit of about 3 dB is achieved. However, the power conversion efficiency of the pump light into the optical signal is not so high as 63% or more.

The 1480 nm band is an excitation band (absorption band).
Is approximately 1450-1500 nm, of which the first-stage amplifiers LD2 and LD3 have a 1460 nm band;
1450-1470 nm is used. Since the bandwidth is relatively wide, an amplifying effect can be obtained even if the wavelength of the pump light is slightly shifted. Although the NF of the amplifier is slightly large at 4.5 dB, the conversion efficiency of the power of the pump light into the optical signal shows a very high value of 95% or more. Use obi.

Returning to the description of FIGS. The optical main signal amplified by the EDF module 1 is an isolator ISO
2 and is input to the gain equalizer GEQ1. The ISO 2 is provided to block the return light from the GEQ 1 and the connector 1. If there is a return light from the GEQ 1 and the connector 1, the EDF 1 reacts sensitively to this return light and oscillates. Therefore, EDF
1 becomes unstable, and the performance of the optical amplifier deteriorates. Therefore, ISO2 is provided in this portion to prevent the operation of EDF1 from becoming unstable. The above-mentioned ISO1 also prevents the return light of the LD2 and LD3 from reaching the connector provided at the input section of the optical in-line amplifier LWAW1 and reflecting it, so that the EDF1 does not oscillate.

GEQ1 is a filter provided to flatten the gain characteristics of the EDF. The gain characteristic of the EDF is 1530, as shown in FIG.
It has a wavy characteristic between nm and 1560 nm. Therefore, when the wavelength (main signal) of each channel to be wavelength-multiplexed is arranged in this wavelength range, the amplification factor at the peak is high and the amplification factor at the valley is low. Therefore, when the wavelength multiplexed main signal is amplified by the EDF, the amplification gain differs for each optical signal of each wavelength, and a level difference occurs between different wavelengths in the amplified wavelength multiplexed light. By the way, an optical signal propagating through a transmission path needs to have a large power to some extent so as not to be buried in noise. , Causing waveform deterioration. Therefore, the optical signal propagated through the transmission path has an upper limit and a lower limit of the optical power for each wavelength, and the power of the optical signal of each wavelength must fall within the upper and lower limits. However, if the power level is different for each wavelength, it is necessary to set the optical signal of the highest wavelength so as not to exceed the upper limit, so that the optical signals of other wavelengths preferably have higher power. Instead, the power cannot be increased to the full upper limit. Therefore, the ratio of signal power to noise (SN ratio) deteriorates for each wavelength, and as a transmission system,
Performance will be bad. However, if the optical signals of all wavelengths are at the same power level,
Since optical signals of all wavelengths can be amplified to just below the upper limit, the performance of the transmission system can be improved. Therefore, the GEQ1 is provided to eliminate the fluctuation of the gain of the EDF due to the change in the wavelength. G
As shown in FIG. 22B, EQ1 is a filter manufactured so that the transmittance is low where the gain of the EDF is large and the transmittance is high where the gain of the EDF is low, and is amplified by the EDF1. By passing the wavelength multiplexed light through such a filter, a gain having substantially flat characteristics as shown in FIG. 22C can be obtained. In this way, the optical output whose gain characteristic is flattened is branched at BS2, and the output light is received at PD2.
The result received by PD2 is the output light level as AGC /
Input to the APC module. The AGC / APC module compares the power at the input terminal to EDF1 previously received by PD1 with the power at the output terminal of EDF1 received by PD2, and adjusts L so that the amplification factor (gain) becomes constant.
The power of the pump light of D1 to D3 is controlled. Thus, the automatic gain control of the EDF 1 is performed by the AGC / APC module. Note that the APC is provided for each of the excitation light sources LD1 to LD1.
3 is controlled so that the output light power is constant, and generally, the back light or the bias current of the LDs 1 to 3 is monitored to control the output light level to be constant. is there.

The reason why the output from the EDF 1 is passed through the GEQ 1 and then fed back to the AGC / APC module is that even if the output whose gain is not flattened is fed back, the power of each wavelength varies and the G
Due to the loss of gain due to EQ1, GEQ1
Accurate AG even if the output before passing through is fed back
This is because C / APC cannot be performed.

The use of the gain equalizer has the following advantages. The wavelength division multiplexing optical amplifiers of FIGS. 19 and 20 can amplify up to 32 wavelength division multiplexed lights.
If all 32 waves are not used, which wavelength optical signal to use depends on the choice of the user who purchases the system and lays it. Therefore, it is not known which wavelength of the optical signal is used. However, if the gain is not flat, the performance of the system differs for each wavelength used, and stable transmission characteristics cannot be provided. . However, using a gain equalizer,
By flattening the gain characteristic of the optical inline amplifier, the amplification gain of the optical in-line amplifier can be made substantially the same regardless of the optical signal of any wavelength, so that stable system performance can be realized.

The reason why the AGC / APC is performed before the optical in-line amplifier is that the power of the optical signal input to the optical in-line amplifier changes depending on the place where the optical in-line amplifier is attached. In other words, the length of the optical fiber between the optical in-line amplifiers used in the optical transmission line may vary depending on the system configuration, and the optical fiber used at present has good transparency. Although the loss is small, the power level of the optical signal input to the optical in-line amplifier is not constant because the optical fiber manufactured in the past has poor transparency and large loss. However, as an optical inline amplifier, the same optical inline amplifier must operate normally regardless of the installation conditions, so it should operate similarly even if the power level of the input wavelength multiplexed optical signal is different. It is. AGC / APC keeps the gain constant even if the level of the input wavelength multiplexed optical signal differs,
The optical signal of each channel can be amplified with almost the same gain. However, even if the gain is constant,
If the input level of the input wavelength multiplexed light is different, the output level of the amplified wavelength multiplexed light output from the EDF will be different. If the output level of the optical in-line amplifier changes due to the difference in input level, a problem arises when designing the system by standardization. Therefore, the main signal (wavelength multiplexed light) passing through the BS2 is input to the variable attenuator (VATT). Is done. Further, when the input power becomes high, the pump is switched from AGC to APC when the pump power reaches the limit. In this case, if the sum of the gains (dB) of the EDFs (EDF1, EDF2, EDF3) is constant, the wavelength characteristic of the gain can be maintained. ).

The variable attenuator provided in the variable attenuator module can adjust the amount of light attenuation by the applied voltage value, and adjusts the output power level of the wavelength multiplexed optical signal amplified by the AGC / APC. be able to. The optical signal that has passed through the variable attenuator
Branched by BS3, one is received by PD3. The power level of the optical signal received by the PD 3 is input to the ALC module, and the power level of the optical signal is adjusted to a constant value. Here, the power level of the optical signal is adjusted by a dispersion compensating module (DCM) connected by the connectors 1 and 2.
Module) dispersion compensating fiber (DCF)
This is for inputting a wavelength multiplexed optical signal having an appropriate power level to a compensating fiber and for stabilizing the operation of the variable attenuator. DCM compensates for waveform deterioration due to dispersion received by an optical signal while propagating through an optical transmission line. In order to effectively compensate for the deterioration of the waveform of the optical signal using the DCF of the DCM, the power level of the input optical signal is large enough not to be buried in noise.
It is necessary to suppress the power level to such an extent that no non-linear effect occurs in the DCF. In particular, the DCF has a core diameter smaller than that of a normal SMF (about 3 to 4 μm), and optical power is concentrated, so that a nonlinear optical effect is likely to occur. Therefore, DC
In order to suppress the nonlinear effect of F, it is necessary to strictly observe the upper limit of the power level of the input optical signal. Therefore, ALC is performed at the BS3 to adjust the power level of the optical signal.

The optical signal input to the DCF is subjected to dispersion compensation, and is input again from the connector 2 to the EDF 2 constituting the subsequent (second) optical amplifier. This optical signal is split by the BS 4 and received by the PD 4. The reception of the input power level of the optical signal here is performed to determine whether or not the DCM is connected to the connectors 1 and 2. That is, if the DCM is removed, the optical signal amplified by the EDF 1 is directly emitted to the outside, which is dangerous. Thus, the PD 4 receives light to determine whether or not the optical signal (wavelength multiplexed light) from the EDF 1 has passed through the DCM. The light reception result is sent to the AGC / APC module, and if the optical signal is being sent, no special processing is performed. However, if the optical signal input level is equal to or lower than a predetermined value, the DCM and the preceding optical amplifier It is determined that one or both of the optical connectors 1 and 2 for connecting the post-stage optical amplifying unit are disconnected, and the amplification factor (gain) of the EDF 1 is reduced to a level at which the intensity of the optical signal is not dangerous. Alternatively, processing such as stopping supply of the pump light from the LDs 1 to 3 and stopping the amplification operation is performed. As a result, even when the DCM is disconnected, the power level of the optical signal output from the connector 1 is reduced, and there is no danger even if an operator is nearby.

The light receiving result of PD4 is shown in FIG.
Input to the module to provide the input optical signal power level for AGC. The main signal that has passed through BS4 is input to optical isolator ISO3 and passes through as it is. I
SO3 determines the light passing direction in one direction so that the EDF 2-1 in FIG. 20 does not oscillate due to the reflected light from the connector 2. The optical signal that has passed through ISO3 is E
It is input to DF2-1 and amplified. The pump light of the EDF 2-1 is supplied from the LD 4 having an oscillation wavelength of 980 nm.
The pump light from the LD 4 is multiplexed into an optical signal by the WDM coupler and sent to the EDF 2-1. Here, as described above, the WDM coupler has a small loss in the case of extremely multiplexing, and is particularly described as 0.98 WDM. ED
In F2-1, amplification is performed only with the 980 nm band pump light. As described above, in the 980 nm band, generation of noise can be suppressed to about the theoretical limit value, which is effective for amplifying a weak optical signal. That is,
Since the optical signal incident on the EDF 2-1 has passed through the DCF having a length of about 10 km first, the optical signal power is attenuated. The DCF has a larger loss than the SMF. For example, in order to compensate for dispersion of about 1000 ps / nm, the loss of the DCF is about 10 dB. E
Since the wavelength-division multiplexed light input to the DF2-1 has been greatly attenuated in this way, amplification using a 980 nm band pump light is performed with noise suppressed. LD4 receives feedback control from the AGC module, and receives EDF2-1
The output power is varied to adjust the gain at.

The optical signal amplified by the EDF 2-1 passes through the optical isolator ISO4 and gain equalizer GEQ
2 is input. The operation of this GEQ2 is as described with reference to FIG. 22, and is for flattening the gain characteristics of the EDF2-1 and the EDF2-2. ISO
Numeral 4 is for preventing the reflected light from the GEQ 2 from being input to the EDF 2-1.
This prevents 2-1 oscillation. GEQ2 to ED
The reason why it is inserted between F2-1 and EDF2-2 is to keep NF (noise figure) low and maintain high conversion efficiency from pump power to signal light power.

The optical signal that has passed through the GEQ 2 passes through the WDM coupler and the optical isolator ISO, and is input to the EDF 2-2. The pump light from the booster BST2, which is the additional pump light source unit in FIG. 19, is input from this WDM coupler. The internal structure of BST2 will be described later.
A BS5 is provided between the connector 3 and the WDM coupler, and the pump light from the additional excitation light source unit BST2 is used to determine whether the pump light from the BST2 is normally incident. A branching path has been created. The pump light branched by the BS5 is received by the PD5 after the power level is adjusted by the attenuator ATT1. The PD 5 obtains the result of whether or not the pump light is normally received from the connector 3 and notifies the BST 2 of the result by a wiring (not shown). In BST2, this result is obtained. If it is determined that the pump light is not received by the PD 5 while the pump light source of the BST 2 emits light, the connector 3 is disconnected and the pump light source is disconnected. It is determined that it is dangerous if the pump light is leaking and there is a person around the pump light, and the excitation light source of the BST 2 is turned off.

From BST2, EDF is performed by the forward excitation method.
The pump light is supplied to 2-2. On the other hand, in the EDF 2-2, a backward pumping method is also used in order to amplify the optical signal into a large output optical signal. That is, LD5 and LD6 having an oscillation wavelength of 1460 nm are provided. These are built-in excitation light sources, and EDF is controlled by the AGC module.
This is for adjusting the gain of 2-2. In addition, a BST 1 as an additional excitation light source unit is attached to the connector 4 in order to obtain a large output optical signal. The internal structure of BST1 will be described later together with the description of BST2.
In order to monitor the attachment / detachment of the connector 4, similarly to the above, a BS 6 is provided, and the pump light from the BST 1 is branched and received by the PD 6 via the attenuator ATT2. Similarly, the result of the light reception is notified to the BST 1 through a wiring (not shown), and when it is determined that the connector 4 is disconnected even though the excitation light source emits light, the excitation light source of the BST 1 is changed to Control to turn off.

Of course, the number of pump LDs of the LDs 5 and 6 and the BSTs 1 and 2 is merely an example, and can be reduced if the required power can be satisfied with a small number of LDs. EDF2-
In No. 2, a 1480 nm band having a high conversion efficiency when converting the energy of the pump light into the energy of the optical signal is used in order to convert the optical signal into a large output signal. Here, the EDF module 2 includes the suspended EDF 2-1 and the subsequent E
DF2-2, and in order to flatten the total gain, the GEQ2
It is common sense to provide
2-1 and EDF2-2. This is because a gain equalizer composed of a filter has a very large loss, for example, a value of 30%. if,
Assuming that a gain equalizer is provided on the output side of the EDF 2-2, as shown in FIG.
2, a large output (for example, an output of about 300 mW when the input to the optical inline amplifier is 1 mW) is obtained.
Even in absolute value, a large loss (for example, 90 mW) is received, and energy for one pump light source LD is wasted.

Therefore, if a gain equalizer is inserted at a stage where the optical signal has not yet become so large, for example, a loss of 10 mW occurs at 100 mW, whereas a loss of 1 mW can be achieved at 10 mW. . For this reason, the gain equalizer is changed to EDF2-1 and EDF2-1.
It is provided in the middle of DF2-2. In addition, the previous GEQ1
Also, the fact that two gain equalizers are provided at two locations in the entire optical in-line amplifier means that the output of each wavelength is aligned before the DCF and input to the DCF with the allowable upper limit of power. Take into account.

Also, since the gains are equalized on the EDF1 side and the EDF2 side, the EDF1 side and the EDF2 side are equalized.
It is easy to adopt a manufacturing method in which the two sides are manufactured separately and then combined later. That is, the output of the EDF 1 is flattened by the gain equalizer, and the main optical signal of each wavelength has uniform characteristics for each wavelength. Also,
The EDF 2 also receives and amplifies the optical signal having the uniform characteristics, and further proceeds with the process of outputting the uniformized optical signal.
1 and the EDF 2 can be easily interfaced. Thus, by arranging the gain equalizer at two places, an advantage in manufacturing can be obtained. Further, the configuration of the wavelength division multiplexing optical amplifier is complicated. For this reason, modularized optical amplifiers (Front Amplifier Part and Rear Amplifier P
Art) and the DCM are configured to be detachable with an optical connector, so that maintenance, inspection, and part replacement can be partially performed, which has a large effect on cost reduction in operation.

The optical signal output from the EDF 2-2 passes through a WDM coupler for multiplexing pump light for backward pumping, and then passes through an isolator ISO5. IS
O5 is provided to block the reflected return light from the output end of the optical in-line amplifier and prevent the EDF 2-2 from oscillating by the return light. The optical signal that has passed through ISO5 passes through a WDM coupler. This WDM coupler does not combine optical signals having different wavelengths, but passes only the main signal, and does not output EDF pump light of EDF2-2, EDF2-1 or EDF1 to the outside of the optical in-line amplifier. Is to do so. That is, light traveling in the direction opposite to the traveling direction of the main optical signal can be blocked by the isolator, but light traveling in the same direction as the optical main signal cannot be blocked by the isolator. Therefore, the WDM coupler is used as a filter that transmits only the main signal so as not to be output outside the optical in-line amplifier.

The optical signal that has passed through the WDM coupler is split by the beam splitter BS7, and one is guided to an output terminal for an optical spectrum analyzer (optical SPA). The optical SPA is attached to this terminal when necessary, and checks whether or not the power levels of the optical signals of the wavelengths (channels) that are wavelength-multiplexed are the same. At present, light S
Since the number of PAs is one, the size is almost the same as that of the optical in-line amplifier shown in FIGS. Therefore, it is necessary to check whether or not the powers of the wavelength-multiplexed optical signals of the respective wavelengths are the same when performing an inspection and adjustment by connecting an optical SPA at the time of upgrade, for example, when increasing the number of wavelength multiplexing. I do.

The optical main signal split at BS7 further includes B
The optical main signal input to S8 and going straight, and OUT PD7
The signal is branched to A junction PD 8 also connected to the BS 8 monitors the reflected light from the output terminal (optical connector 5) of the optical in-line amplifier.
LD4, LD4
5, a control signal is supplied to the LD 6 and the pumping light sources of the BSTs 1 and 2 to lower the output and lower the gain of the EDF 2. The EDF2 is controlled so that the power of the optical signal output from the output terminal of the optical in-line amplifier becomes smaller than about 10 mW.
To control the gain.

Out of the optical signals branched by BS8, OUT
The intensity of the optical signal received by the PD 7 is converted into an electric signal, and is fed back to the AGC module.
AGC is performed along with the optical signal from the ALC module, and is fed back to the ALC module to control the amount of attenuation of the variable ATT, thereby performing ALC. This ALC keeps the output power of the optical in-line amplifier constant. Thus, the feedback from the PD 3 and the feedback from the OUT PD 7 are applied to the ALC doubly.

As for the feedback from the OUT PD 7 to the AGC module, the gain is detected together with the feedback from the PD 4, and LD 4, LD 5, LD
6, and control of the excitation light sources of BST1 and BST2 described later is performed.

The optical main signal (amplified wavelength-division multiplexed light) output without being branched from the BS 8 is multiplexed with the SV signal separately processed by the subsequent WDM coupler, and output from the output terminal of the optical in-line amplifier. Is done.

The connectors 3 and 4 can be connected to BST2 and BST1, which are excitation light source units, respectively. BST1 and BST2 are
When the power of the pump light is insufficient with the built-in laser diode LD, it is separately connected and used. For example, when the number of multiplexed wavelengths (the number of channels) is between 1 and 8, the built-in LD can provide pump light with sufficient power. When the number of multiplexed wavelengths (the number of channels) is 9 to 16, BST1 is connected and used. When the number of multiplexed wavelengths is 17 to 32, BST1 and BST2 are connected and used together.

As the pumping light source included in the BST 1, LD7 and LD8 having an oscillation wavelength of 1480 nm having different polarizations and an output of 140 mW are used. The pump lights having different polarizations output from the LD 7 and LD 8 are polarization-synthesized by the PBS of the polarization beam splitter, and output to the outside of the BST 1 via the pigtail fiber code. Since the powers of the pump lights of the LDs output with different polarizations are approximately 1 + 1 = 2 by the polarization combining, the advantage of providing a plurality of LDs can be effectively used.

The oscillation wavelengths of the LDs 7 and 8 of the BST 1 are different from the oscillation wavelengths of the built-in LDs 5 and 6.
The wavelengths are multiplexed (multiplexed) by the WDM coupler of the PBS module. This is the same, and when trying to combine pump lights of the same wavelength, the output of the combined pump light is not necessarily the sum of both powers due to the phase difference between them. However, if pump lights having different wavelengths are combined by a WDM coupler, ideally, 1 + 1 = 2
Holds, and pump light having a power close to the sum of all the optical powers from the LD can be obtained.

Here, the oscillation wavelengths of the LDs 5 and 6 and the LDs 7 and 8 are different from each other.
It has a wide absorption band in the 80nm band and 1460n
Both the pump light of m and the pump light of 1480 nm are absorbed in the same band, and can be used as the pump light. As described above, the WDM coupler multiplexes the pump lights having different wavelengths to obtain a high-output pump light, and it is possible to obtain an optical signal amplifying action in the same EDF operating band. FIG. 24 illustrates this state.

When the output lights of the LD 7 and LD 8 are multiplexed by the PBS, the light is then split by the beam splitter 9 and received by the PD 7 via the attenuator ATT3.
The PD 7 monitors whether or not the output levels of the LDs 7 and 8 of the BST 1 are normal. Also, BS
In order to determine whether or not the connector 4 of the pigtail fiber cord of T1 is disconnected, it is also monitored whether or not the power level of the pump light obtained by multiplexing the outputs of the LDs 7 and 8 is smaller than about 10 mW. Connector 4
Is determined as a result of receiving light at PD6,
Since the AGC module instructs each LD to weaken the output, for EDF Md1,
The level of APC of the excitation light sources LD1 to LD3 is set to a low value.

In BST1, the same oscillation wavelength (1480n
m) The excitation light sources LD7 and LD8 are polarized and synthesized by PBS,
Provides excitation light. And to simplify the configuration,
AGC is performed simply by turning on / off the LDs 7 and 8.
And ALC was not performed. When the output power of a semiconductor laser having an oscillation wavelength of 1480 nm is small, the oscillation wavelength shifts to the shorter wavelength side. For example, if the oscillation wavelength is 14
If the wavelength shifts to around 60 nm, the WDM coupler prevents wavelength multiplexing with LDs 5 and 6 having an oscillation wavelength of 1460 nm. That is, as described above, this WDM coupler is connected to the 1
Since the pump light of 480 nm is designed to be input to the EDF 2-2, the pump light of the wavelength of 1460 nm from the BST 1 cannot be efficiently input to the EDF 2-2. Therefore, the LDs 7 and 8 always output the pump light having the maximum power, and set the oscillation wavelength to 1480.
Stabilize to nm. For example, when the number of channels is 9 to 12, only the LD 7 may be operated at the maximum power, and when the number of channels is 13 to 16, the LD 7 and the LD 8 may be controlled to operate at the maximum power. Adjustment of the excitation power can be realized by controlling the output power of the built-in LDs 5 and 6 by the AGC module.

The BST 2 includes LDs 9 and 10 having an oscillation wavelength of 1460 nm and an output of 140 mW, and LDs 11 and 12 having an oscillation wavelength of 1480 nm and an output of 140 mW. The LD9 and LD10 and the LD11 and LD12 have different polarizations, respectively, and are polarization-synthesized by PBS.
Further, the outputs of the LD 9 and LD 10 are polarization-combined,
LD11 and LD12 obtained by combining polarizations are combined by a WDM coupler and output. Also in the BST2, the multiplexed pump light is branched by the BS 10 and the attenuator ATT
4, the light is received by the PD 10. And PD10
It is determined from the result of the light reception that the respective LDs are operating normally. Most of the pump light not split by the BS 10 is sent to the EDF 2-2 via the connector 3. Also here, the PD 5 determines whether or not the connector 3 is properly connected. If it is determined that the connector 3 is disconnected, the LD 9 controls the LD 12 to control the pump light output from the BST 2. However, the power is reduced to a power that is not dangerous even if it enters the eyes of the operator. At this time, the output power of BST2 is detected by P
D10.

As for BST2, the total pump power after wavelength multiplexing is monitored by PD10,
There is no problem in ST1, and the LD9 to LD12 may always be driven simultaneously and the input level to the PD 10 may be set to four levels.

When BST1 or BST1 and BST2 are connected, control for keeping the gain constant from the AGC module is performed.
The control of the LD in T2 is performed only when the LD is turned on or off.
This is done by adjusting the output of

[0108] Further, it is conceivable that a plurality of BST1s and BST2s are put in one shelf or the like and connected to an optical in-line amplifier. It is very likely that In such a case, initially, the booster BST
The pump light is output with an output smaller than 10 mW and is at a level that does not cause any problem even if it enters the eyes of an operator. When this is connected to the optical in-line amplifier, it is detected by PD5 and PD6, and it is recognized that the connectors 3 and 4 are connected. Then, the AGC module issues an instruction to further increase the output level of the pump light. If the connection of the pump light and the connection of the electrical wiring are made from the same BST to the same optical in-line amplifier, there is no problem even if the output level of the pump light is maximized at this stage, but if the connection is made incorrectly In this case, an instruction to increase the output of the pump light is issued to the BST to which the pump light is not input to the optical in-line amplifier. BS instructed by electrical connection
If the pump light of T is not connected to the same optical in-line amplifier, the pump light will be input to another optical in-line amplifier, and the operation will be strange. Also, if the pigtail fiber cord is not connected anywhere, the pump light with high intensity will leak to the outside, which is dangerous if it enters the eyes of an operator.

Therefore, when the optical in-line amplifier detects the connection of the BST, the power of the pump light is slightly increased with a power that is not dangerous even if it leaks outside (for example, a safe light state of 10 mW or less). . In response to the instruction to increase the power of the pump light, if the power of the pump light actually increases slightly, the optical in-line amplifier determines that the pigtail fiber cord connection and electrical connection have been made normally, and the BST Then, the BST is instructed to maximize the power of the pump light.

As described above, when the BST is connected, the power of the pump light is set to two levels within the range of the power (safety light state) that is not dangerous to the operator, so that the connection is normal on the optical in-line amplifier side. The procedure to maximize the power of the pump light after confirming that the pump power is extremely high, the dangerous pump light with a very high power leaks to the outside, or the wrong optical in-line amplifier It is possible to avoid a situation in which the input is not noticed as it is input to the.

In the optical in-line amplifier shown in FIGS.
The output of the optical signal is configured to monitor the entire power using a PD. Therefore, the following problem occurs when the number of wavelength multiplexes is increased. That is, there is an upper limit and a lower limit in the power level of each wavelength of the optical signal propagated through the optical transmission line, but it is assumed that the transmission is performed by four-wave multiplexing at the initial installation stage. In this case, the power of each optical signal of four different wavelengths is transmitted such that it falls between the upper limit and the lower limit of the transmission path. Here, if the number of multiplexed wavelengths is upgraded to, for example, eight waves, the optical in-line amplifier monitors the entire power of the wavelength-multiplexed optical signal. As the total power of the optical signal increases, the power of the optical signal of each wavelength is suppressed by ALC. As a result, the power of the optical signal of each wavelength may fall below the lower limit of the transmission path. In this case, the performance of the transmission system cannot be maintained. Therefore, when increasing the number of multiplexed wavelengths, an SV signal is used to notify each optical in-line amplifier that the number of multiplexed wavelengths will increase. The optical inline amplifier receiving this stops the ALC when the number of multiplexed wavelengths increases. Since the optical in-line amplifier operates as an AGC amplifier, it amplifies an optical signal with a constant gain even if the number of wavelength multiplexes increases. Then, the ALC is restarted, and the power level of the optical signal is reset to a predetermined value. The power level to be set of the entire optical signal in the case of a new wavelength multiplexing number is set in the ALC module via the SV signal. By doing so, it is possible to cope with an increase in the number of multiplexed wavelengths without providing any new configuration.

Also, it is necessary to increase the power of the pump light as the number of wavelength multiplexes increases. However, in the present optical in-line amplifier, amplification in the 980 nm band having a good noise characteristic (noise figure; NF) is first performed. In addition, if high power pump light is required,
Amplification is performed using the nm band. FIG. 25 shows this state. In FIG. 25, EDF
The distance is taken on the horizontal axis from the input port to the output port, and the vertical axis shows the power of the amplified optical signal. As shown in the figure, what is described on the figure is 9
The state of the excitation light in the 80 nm band and the state of the excitation light in the 1480 nm band are shown. Since the pumping light in the 980 nm band is forward pumping, it is incident from the input port of the EDF and is consumed as going backward. Further, since the pumping light in the 1480 nm band is backward pumping, it is incident from the output port of the EDF toward the input port, and the pump light is consumed as going forward. On the other hand, since the optical signal propagates from the input port to the output port, the power is gradually amplified toward the output port. As described above, after sufficient amplification in the 980 nm band is performed, the insufficient portion is further amplified in the 1480 nm band, so that an optical signal with good noise characteristics can be amplified.

The configuration of the optical in-line amplifier described with reference to FIGS. 19 and 20 is similarly applied to an optical post-amplifier and an optical pre-amplifier. However, in the case of an optical post amplifier, SV
WDM1 for demultiplexing a signal from a wavelength-division multiplexed optical signal on the input side
2, and the optical preamplifier does not include the WDM 3 that combines the SV signal with the wavelength division multiplexed optical signal on the output side.

Next, the control circuit for the wavelength division multiplexing optical amplifier described in FIGS. 19 and 20, particularly the optical in-line amplifier LWAW1, will be described with reference to FIG. The next monitor signal is input to the optical signal monitor circuit 120. 1) Optical input level to the pre-stage optical amplifier detected by PD1 2) Optical output level from the pre-stage optical amplifier detected by PD2 3) Variable optical attenuator module VAT detected by PD3
T optical output level (optical input level to DCM) 4) optical input level to optical amplifier at the subsequent stage detected by PD4 (optical output level from DCM) 5) reflected light from optical connector detected by PD8 Level 6) Optical output level from the post-stage optical amplifying unit detected by OUT PD7 7) Excitation light detection signals from the additional excitation light source units BST1 and BST2 detected by PD6 and PD10 AGC results
The bias voltage of each of the LDs 1 to 3 of the excitation light source module 121 is controlled by the bias voltage control circuit 122 and input to the control circuit 132 constituting the / APC module.
1 to 3 are controlled. Also, the temperature control circuit 1
23 controls the temperature of each of the LDs 1 to 3 to be constant. The preamplifier and V detected by the optical signal monitor circuit 120
The AT monitor signal is supplied to the analog / digital conversion circuit 1
The data is input to the CPU 131 via the CPU 24. Also, a bias voltage value is input from the bias voltage control circuit 122, and outside air temperature information is input from the outside air temperature sensor 124 to the A / D converter circuit 124. The AGC module of the post-stage optical amplifier operates in a similar manner.

The CPU 131 processes various kinds of monitor information input from the I / O port, and outputs an operation state, an alarm signal, monitor information, and the like as a monitor control signal to the optical service channel interface OSCIW1. Further, the CPU 131 analyzes the monitoring control information received from the OSCIW 1 and bias control circuits 122 and 12 to turn on / off the excitation light source modules 121 and 133.
7 and a start signal of the temperature control circuits 123 and 128 are output.

Next, the operation of the CPU 131 for controlling the optical in-line amplifier LWAW1 will be described with reference to the state transition diagrams of FIGS. The CPU 131 performs state control of a WDM optical amplifier capable of amplifying a 32-channel wavelength-division multiplexed optical signal, various types of monitoring / monitoring, and communication with the outside (specifically, communication of monitoring control information via the OSC). .
In the wavelength division multiplexing transmission system of FIG. 1, different information (OC-192, OC-48, etc.) is placed on a plurality of wavelengths (channels), these are wavelength multiplexed, and one single mode optical fiber is used. This is a transmission method, and the transmission capacity can be dramatically increased. An optical amplifier applied to this system is required to have a function of amplifying each wavelength with equal gain. In addition, the number of wavelengths (the number of channels) must be increased and
Removal (for example, if the transmission capacity of each channel is 2.4 Gbps
Must be removed when upgrading from 10Gbps to 10Gbps. ) Is required, and a function that allows the number of channels to be added or removed during operation (in-service upgradeability) is also required. The operating states and transitions of the CPU 131 applicable to these will be described with reference to FIGS. A. Power-off state: Power supply of the optical amplifier unit is off. Input cutoff state: the input of the optical amplifier is equal to or lower than the input recovery threshold, and the pump light source LD1 of the pre-amplifier and the post-amplifier
~ 3, LD4 ~ 6 are not energized. C. Pre-stage safety light state: EDF module 1 of pre-stage amplifier
Has reached the set value (AGC set voltage), but the output is at the safe light level. If the DCM is not connected or the connection of the optical connectors 1 and 2 is poor and the input level of the post-amplifying unit is less than the input recovery threshold, the pump light source L of the post-amplifying unit
D4 to 6 are stopped. BST1 and BST2 are also stopped. D. Safety light state: the output connector 5 of the optical amplifier is in the open state, and the optical output power is controlled to a level safe for the human body. Laser Safety function is ON
In this case, this state is set.
When Safety Inhibit is received, the state transition does not have the safe light state as shown in FIG. Safety light OFF
The state transition diagram of (Laser Safety Inhibit) is as follows when transitioning from the safe light state to the ALC state.
This corresponds to transition to the normal light state without detecting connection / disconnection of the output connector 5 in the state transition diagram of the safety light ON (Laser Safety ON). BST1,2
Has stopped. The safe light ON / OFF is received even in the safe light state and the normal light state, and is reflected in the operation of the optical amplifier. E1. ALC state: a state in which communication is actually possible (normal optical state), and a state in which the (total) output constant control is performed by the interruption variable optical attenuator based on the wavelength number information and the optical amplifier number. E2. AGC state: A state in which the attenuation of the variable optical attenuator ATT is fixed, and the AGC / APC module and the AGC module control the front-stage EDF module 1 and the rear-stage EDF module 2 to operate at a constant gain. In the ALC state, the operation of the variable optical attenuator ATT controls the total output of the wavelength-division multiplexed optical signal at the output terminal to be constant, but in this state, it is fixed to the average value (freeze state). ). If the number of wavelengths (the number of channels) is added / removed later than the AGC control speed, the operation is constant gain, so that the output of the surviving channel (the channel that continues the service) is not affected. This is one of the normal light conditions.

Further, the additional excitation light source module BST1
And BST2 are added / removed in this AGC state. The operation at the time of extension is as described with reference to FIGS. Each state and state transition will be described in more detail. (1) Transition from power-off state to input-off state: power is supplied to the optical amplifier unit, resetting of each electronic component, provisioning from OSC (operation information), Condition
ioning (condition setting) is received, and initialization setting is performed. Further, the temperature control of the pump light source LD requires time to reach a constant value, and thus is started at this stage. (2) Input disconnected state: input power to the optical amplifier (PD1
Is less than or equal to the input recovery threshold set by hardware, and
1 is a state in which the input disconnection signal is output. Alternatively, the excitation light sources LD1 to LD1 of the first-stage optical amplification unit and the second-stage optical amplification unit
3. No bias current is supplied to LDs 4-6.

When detecting the input disconnection signal, the CPU 131 detects an alarm signal LOL (Lossof Light).
Is output to OSCIW1. Note that the threshold value for input recovery depends on the number of channels. When the number of channels is 0 as a result of reading the number of channels in the input disconnected state, the CPU 131 holds the input disconnected state.

(3) Transition from the input disconnected state to the preceding safety light state: It is detected that the optical input from PD1 is equal to or larger than the input recovery value. The supply of the bias current to the pump light sources LD1 to LD3 of the preamplifier is started. The time constant of the AGC / APC module is set so that the gain of the front-stage EDF 1 gradually reaches the set value.

The ALC module has a variable attenuator ATT
Of the variable attenuator ATT is controlled so as to gradually reach the safe light level. Since the output level setting (attenuation amount) of the variable attenuator ATT is set to a level (safety light) that is safe for the human body, even if DCM is not connected, the light at a dangerous level for the human body is not emitted to the space. Considered. In this transition,
No bias current is supplied to the pump light sources LD4 to LD6 in the rear amplification unit.

(4) Pre-stage safety light state: The gain of the pre-stage EDF 1 has reached the set value (AGC set voltage), but the output level is controlled to the safe light level by the ALC module. A state in which the DCM is not connected or the connection is poor, and the input level to the subsequent EDF2 is less than the input recovery threshold, and the operation of the pump light sources LD4 to LD6 of the subsequent EDF2 is stopped.

(5) Transition from pre-stage safety light state to safe light state: It is detected that the input level to the post-stage amplification unit detected by PD4 has exceeded the input recovery threshold value.

To compensate for the DCF loss, the ALC
The attenuation of the variable attenuator ATT is adjusted by the module. Specifically, the reference value (dBm / c) of the input level to the subsequent stage
h, for example, −12 dBm / ch) and the amount of attenuation is adjusted so that the optical monitor value to the subsequent stage becomes equal. If the number of wavelengths is 4, -6 dBm (= -12 + 6).

[0124] The AGC module allows the subsequent EDF2
Supply of bias current to the excitation light sources LD4 to LD6 starts. A
The GC module gradually increases the gain of the post-stage EDF2. The safety light setting voltage is set so that the output level of the latter-stage EDF 2 is maintained at the safe light level. AG
The C module has two reference values, a safe light setting voltage and an AGC setting voltage, and drives the excitation LD through an analog maximum value circuit.

(6) Transition from the safe light state to the ALC state: OUT When the ratio between the output light power detected by the PD 7 and the reflected light power detected by the PD 8 exceeds a set value (when the reflected light power decreases). Next, the connection of the optical connector 5 on the output side is detected.

The AGC set voltage is gradually increased to a predetermined value. Release the safety light setting voltage. (7) Transition from ALC state to AGC: A switching signal to AGC mode is received from the optical service channel.

Variable attenuator AT at the time of receiving the switching signal
T attenuation is fixed by ALC module. The optical amplifier operates in an AGC mode (constant gain control mode).

[0128] Information on the number of wavelengths (number of channels) is received from the OSC. Check whether additional pump light source modules BST1 and BST2 are added or removed. OSC, BST
1, Notify the connection of BST2.

Based on the completion of the addition / removal of the number of wavelengths (the number of channels), the OSC detects that the signal for switching to the AGC mode has been turned off. Update to ALC set voltage according to the number of wavelengths (number of channels) and output from ALC module. Also, the input level and output level thresholds are updated according to the number of wavelengths, and ALC control is started by the ALC module.

(8) Transition from the ALC state to the safe light state: OUT The ratio of the output light power detected by the PD 7 to the reflected light power detected by the PD 8 becomes equal to or less than a set value (when the reflected light power increases). In the case, the optical connector 5 on the output side
Detected open.

The safety light setting voltage of the AGC module of the latter stage EDF2 is turned ON. The AGC set voltage of the AGC module of the latter stage EDF2 is reduced (turned off).

(9) AGC state → Safety light state: OUT When the ratio of the output light power detected by PD7 to the reflected light power detected by PD8 becomes equal to or less than a set value (when the reflected light power increases), Output side optical connector 5
Detected open.

The safety light set voltage of the AGC module of the latter EDF2 is turned ON. The AGC set voltage of the AGC module of the latter stage EDF2 is reduced (turned off).

(10) Each state → input disconnected state (Shutd
own) If the input level from PD1 becomes equal to or less than the threshold value, input disconnection is detected.

The AGC setting voltage of the AGC module is set to zero. Set the safety light setting voltage of the ALC module to zero. Set the AGC setting voltage of the AGC / APC module to zero.

Set the ALC setting voltage of the ALC module to zero. Now, a sequence in the case of adding / removing a channel using the optical service channel OSC in the wavelength division multiplexing system of FIG. 1 will be described with reference to FIGS.

In the wavelength division multiplexing system of FIG. 1, the addition / removal of a channel is controlled online (in-service state) by the DS1 frame (FIG. 11) of the optical service channel OSC having a wavelength of 1510 nm. Channel expansion
The control signal for removal is the OSC-A of the DS1 frame.
It is transmitted using the IS byte (time slot 9).
The contents of this OSC-AIS byte are shown in FIGS. FIGS. 31 to 36 show the operation sequence of each optical amplifier (TWAA, LWAW1 to 3, and RWAB) at the time of channel addition / removal. The operation flowchart is shown in FIGS.

First, when adding / removing a channel, the operator uses the console of the wavelength division multiplexing / demultiplexing apparatus WMUXA to select the bit rate of channels 1 to 32 (2.4 Gbps).
Or 10 Gbps), and Provisioning information (operation information) indicating whether the channels 1 to 32 are in the in-service (IS) state or the out-of-service (OOS) state, and updates the operation information of the channel to be added or removed.
(S1 in FIG. 37, FIG. 31) These operation information are stored in the O of the wavelength division multiplexer WMUXA.
SC interface OSCIA). OS
The CIA converts the bit rate information (WCR) and IS / OOS information (WCS) of each channel into a WCR byte and a WCR byte in the multi-frame byte of the time slot 23 of the OSC.
Using the SC byte, each of the optical repeaters 1 to 3 and each of the OSCIW1 to 3 and OSCW of the wavelength multiplexing / demultiplexing apparatus WMUXB of the opposite station are used.
While transmitting to IB, as shown in FIGS.
Using the command c of the OSC-AIS byte, the change of the WCR and WCS bytes is notified.

Next, the operator uses the console to
A command for shifting each optical amplifier (TWAA, LWAW1-3, RWAB) from the ALC mode to the AGC mode is input. This command is transmitted to the OSCIA and the CPU of the TWAA. The optical post-amplifier TWAA shifts from the ALC mode to the AGC mode. OSCIA operates as shown in FIGS.
Bit b of OSC-AIS byte of DS1 frame of C
2 to b5 are set in a predetermined pattern, and each optical amplifier (LWA
W1 to W3) and optical service channel interfaces OSCIW1 to 3 (RWAB).
(S2 in FIGS. 32 and 37 to 39) Optical service channel interface OSCIW1 to 3
And OSCIB are b2 to b5 of the OSC-AIS byte.
Is notified to the CPU of each optical amplifier. CPU is A
When a transition command from the LC mode to the AGC mode is detected, transition from the ALC mode to the AGC mode is controlled. Each of the optical repeaters 1 to 3 and the wavelength division multiplexer WMUXB
When the shift of the optical in-line amplifiers LWAW1 to 3 and the optical preamplifier RWAB to the AGC mode is completed,
The WMUXA is notified using the DCC bytes of the OSC time slots 5 to 6. (S3 in FIGS. 33 and 37 to 39) The MCA unit determines whether it is necessary to add or remove the additional pumping light sources BST1 and BST2 of each optical amplifier when adding or removing the number of channels. OS if necessary
Using the command d of the C-AIS byte, each optical repeater 1
BST1 and BST2 instruct the wavelength division multiplexing / demultiplexing apparatus WMUXB to confirm the connection. In addition, the own device (WMUX
Excitation light source BST for extension of optical post-amplifier TWAA of A)
Check the connection status by using the optical post-amplifier TWAA CP.
Instruct U. For example, when the number of channels is 1 to 8,
Only the power of the pump light from the built-in pump light sources LD1 to LD6 is used.
In addition to the above, it is necessary to operate the additional pumping light source BST1 to increase the pumping light power, and when the number of channels is 17 to 32, BST1 and BST2
It is necessary to operate both. Each optical repeater 1
The connection confirmation information of the BSTs 1 and 2 of the optical in-line amplifiers LWAW1 to LWAW3 is transmitted using the DCC byte of the OSC and the management device MCA of the wavelength multiplexing / demultiplexing device WMUXA.
Confirmed by. (S4 in FIGS. 37 to 39) Next, channel addition / removal is actually performed. (S5 in FIGS. 34 and 37 to 39) Next, the SA of the wavelength division multiplexing / demultiplexing apparatuses WMUXA and WMUXB is described.
The UA and SAUB CPUs update the setting values based on the new channel information. Then, the optical variable attenuators VATA1 to 32 and V corresponding to the channels to be added or removed
The attenuation of the ATBs 1 to 32 is maximized, and the SAUA confirms that this channel is in the input disconnected state. After the confirmation, the attenuation amounts of the variable optical attenuators VATA1 to 32 and VATB1 to 32 of the wavelength demultiplexers WMUXA and WMUXB are measured by the spectrum analyzers SAUA and SAUB.
CPU and optical variable attenuator unit VATA, VATB
And is set to an optimal value. (FIG. 3
S6 to S9 of 7 to 39) The MCA transmits a command to update the wavelength (channel) information to each of the optical repeaters 1 to 3 and the wavelength division multiplexing / demultiplexing apparatus B. This command is issued by OSCIA
Sent by OSC as a command g of SC-AIS byte. The optical repeaters 1 to 3 and the wavelength multiplexing / demultiplexing device WMUXB, including the wavelength multiplexing / demultiplexing device WMUXA,
The channel information is updated using the information of the CS byte.
The various threshold values and set values used by the CPU of the optical amplifier described in FIGS. 26 to 28 are also changed based on the updated channel information. (S11 in FIGS. 37 to 39) Each of the optical repeaters 1 to 3 and the wavelength multiplexing / demultiplexing device WMUXB are:
The MCA is notified of the confirmation of preparation for transition to the ALC mode using the DCC byte of the OSC. (S1 in FIGS. 37 to 39)
2) Next, the management device MCA instructs the all-optical amplifier to shift from the AGC mode to the ALC mode. The notification from the AGC mode to the ALC mode is performed using the command h of the OSC-AIS byte of the OSC. CPU of each optical amplifier
Receives the command h from the OSC,
The mode is controlled to shift from the mode to the ALC mode. A
When the transition to the LC mode is completed, each of the optical repeaters 1 to 3 and the wavelength division multiplexing / demultiplexing device WMUXB use the DCC of the OSC to instruct the MSCA to return to the ALC mode,
That is, it notifies that each optical amplifier is operating in the normal optical state. (S13 in FIGS. 35 and 37 to 39) In each of the optical repeaters 1 to 3, a failure of the optical service channel OSC (monitoring control optical signal loss (Loss Of L)
right), no monitoring control channel (Loss Of)
(Facility), detection of a reception error by a parity check bit), a flag is set in the b1 bit of the OSC-AIS byte, and the flag is notified to the downstream side.

[0140]

As described in detail above, according to the present invention, it is possible to provide an optical amplifier which has solved various problems required for a wavelength division multiplexing optical communication system.

This optical amplifier is modularized into a pre-stage optical amplification unit and a post-stage optical amplification unit. Even if an optical component is shared for each module and manufactured, an optical coupling means such as an optical connector is required. By connecting via the optical amplifier, a completed optical amplifier can be assembled. In addition, maintenance and inspection can be performed by dividing the module into each module, so that a failure location can be easily searched.

In the above description, wavelength multiplexed optical signals have been described as an example, but it is needless to say that the optical amplifier of the present invention can be applied to optical signals of a single wavelength.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of a wavelength division multiplexing transmission system.

FIG. 2 is a diagram showing a SONET STS-1 frame format.

FIG. 3 shows a section overhead (SOH) and a line overhead (LO) of an STS-1 frame format.
It is a figure for explaining H).

FIG. 4 is a diagram illustrating byte allocation of an overhead part of an STS-1 frame.

FIG. 5 is a diagram for describing an STS-n frame obtained by multiplexing an STS-1 frame by n frame bytes.

FIG. 6 is a diagram showing a frame format of OC-192 (STS-192).

FIG. 7 is a diagram for explaining a wavelength arrangement (channel arrangement) of optical signals of respective wavelengths in the wavelength division multiplexing system of FIG. 1;

FIG. 8 is a diagram showing a basic configuration of wavelength division multiplexers WMUXA and WMUXB.

FIG. 9 is a diagram showing a basic configuration of optical in-line amplifiers LWAW1 to 3;

10 is a diagram showing a basic configuration of a transponder for wavelength-converting an optical signal wavelength of an existing transmission device according to the channel arrangement of FIG. 6;

FIG. 11 is a diagram showing a frame format of an optical service channel.

FIG. 12 is a diagram for explaining the contents of byte information inserted into each time slot of the optical service channel OSC.

FIG. 13 is a diagram for explaining a configuration of one multi-frame of multi-frame bytes in the tyoslot 23 of the optical service channel OSC.

FIG. 14 is a diagram illustrating a basic configuration of a signal receiving unit of the optical service channel interface OSCIA of the wavelength division multiplexing / demultiplexing apparatus.

FIG. 15 is a diagram illustrating a basic configuration of a signal transmission unit of the optical service channel interface OSCIA of the wavelength division multiplexing / demultiplexing apparatus.

FIG. 16 is a diagram showing a basic configuration of an optical service channel interface OSCI of the optical repeater.

FIG. 17 shows RWAA, TWAA and L of FIGS.
OSC interface OSCI provided in WAW1
FIG. 3B is a diagram illustrating an interface between OSCIA, OSCIA, OSCIW1 and an overhead serial interface OHS.

FIG. 18 is a diagram for explaining the relationship between optical signal power and noise in the wavelength division multiplexing transmission system of FIG.

FIG. 19 is a diagram (part 1) illustrating a specific configuration of an optical amplifier.

FIG. 20 is a diagram (part 2) illustrating a specific configuration of the optical amplifier.

FIG. 21 is a diagram (part 1) for explaining the operation of the optical amplifier;

FIG. 22 is a diagram (part 2) for explaining the operation of the optical amplifier;

FIG. 23 is a diagram (part 3) for explaining the operation of the optical amplifier;

FIG. 24 is a diagram (part 4) for explaining the operation of the optical amplifier;

FIG. 25 is a view (No. 5) for describing the operation of the optical amplifier.

FIG. 26 is a diagram for explaining a configuration of a control unit of the optical amplifier in FIGS. 19 and 20;

FIG. 27 is a diagram (part 1) for explaining the operation of the control unit of the optical amplifier;

FIG. 28 is a diagram (part 2) for explaining the operation of the control unit of the optical amplifier;

FIG. 29: OS used when adding or removing channels
Diagram for explaining details of monitoring control information of C (part 1)
It is.

FIG. 30: OS used when adding / removing the number of channels
Diagram for explaining details of monitoring control information of C (part 2)
It is.

FIG. 31 is a diagram (No. 1) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

FIG. 32 is a diagram (part 2) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

FIG. 33 is a diagram (part 3) for explaining the operation sequence of each optical amplifier when the number of channels is increased / removed.

FIG. 34 is a diagram (No. 4) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

FIG. 35 is a view (No. 5) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

FIG. 36 is a diagram (No. 6) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

FIG. 37 is a diagram (No. 7) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

FIG. 38 is a diagram (No. 8) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

FIG. 39 is a diagram (No. 9) for explaining the operation sequence of each optical amplifying device when the number of channels is increased / removed.

[Explanation of symbols]

10 Overhead 11 SOH 12 LOH 13 Pointer Byte 20 Payload 2-1 Variable Optical Attenuator 2-2 Monitor 2-3, 4-1, 5-1, 6-1 and 31-5 CP
U 2-4, 4-3 OSCIA 2-5 Coupler 3-1 Multiplexer 4-2 Electric / optical converter 4-4, 4-5, 6-4, 6-5 Optical amplifier 4-6, 4-7 , 6-6 Coupler 5-2 Spectrum analyzer 6-2 Optical / electrical conversion unit 6-3 OSCIB 7-1 Demultiplexer 8-1, 32-1, 33-3, 42-1, 43-3
Photoelectric conversion unit 8-2, 9-3, 32-2, 42-2 HUB 8-3, 32-3, 41-3, 42-3 OHS 8-4, 32-4, 42-4 Monitor 8-5 , 32-5, 42-5 Alarm generator 9-1, 33-1, 43-1 PCI 31-1 Preamplifier 31-2 Postamplifier 31-3, 41-1 Optical / electrical converter 31-4, 41- 2 Electrical / optical converter 31-6 OSCIW1 52, 92 CMI decoder 53, 94 Frame synchronizer 54, 78, 93, 106 PG 55, 95 Protector 56, 75, 96, 103 BIP operation unit 57, 98 Comparison unit 58 , 97 Demultiplexer 59, 99 Holder 60, 100 Three-stage protector 61, 102 Selector 71 Check processor 72, 104 Multiplexer 73 provision 74 Condition monitoring 76 multiplexer 77, 107 digital PLL 79, 105 frame generation unit 80, 108 CMI coding unit 120 optical signal monitoring circuit 121, 126 excitation LD module 122, 127 bias control circuit 123, 128 temperature control circuit 124, 129 external temperature sensor 125, 130 AD / DA converter

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04B 10/17 10/16 (72) Inventor Yasushi Sugaya 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Fujitsu Limited (72) Inventor Chihiro Oshima 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Terumi Chikuma 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (72) Inventor Hiroyuki Ito 2-1-1 Kita-Ichijo-Nishi, Chuo-ku, Sapporo, Hokkaido Within Fujitsu Hokkaido Digital Technology Co., Ltd. Fujitsu Limited (72) Inventor Daiki Kobayashi 4-1-1, Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Fujitsu Limited

Claims (3)

[Claims] An optical fiber doped with a rare earth element, a pre-stage optical amplifier having an excitation light source for inputting excitation light to the optical fiber, a second optical fiber doped with a rare earth element, A post-amplifier having a pump light source for inputting pump light to the optical fiber, wherein the pre-amplifier and the post-amplifier are optically connected via detachable optical coupling means. Characteristic optical amplifier. 2. An optical fiber doped with a rare earth element to which a plurality of wavelength-division multiplexed optical signals having different wavelengths are inputted, and a wavelength dependency of a gain characteristic of the optical fiber provided on an output side of the optical fiber. A pre-amplifier having a gain equalizing means for performing the operation, and a post-amplifier having a second optical fiber doped with a rare earth element, wherein the pre-amplifier and the post-amplifier are detachable light. An optical amplifier, which is optically connected via coupling means. 3. A pre-stage optical amplifier having a rare-earth element-doped optical fiber to which wavelength-multiplexed optical signals of a plurality of different wavelengths are inputted, and outputting an amplified optical signal; and an output from the pre-stage optical amplifier. A dispersion compensating means for compensating and outputting the dispersion of each of the optical signals, and a second optical fiber doped with a rare earth element to which each optical signal outputted from the dispersion compensating means is inputted; Gain equalizing means provided on the output side of the optical fiber to compensate for the wavelength dependence of the gain characteristic of the second optical fiber,
A second optical amplifier having a third optical fiber doped with a rare earth element to which each optical signal output from the gain equalizing means is input.