JPH05199183A - Fiber light amplifier repeater - Google Patents

Abstract

PURPOSE:To provide the fiber light amplifier repeater using a fiber light amplifier capable of sending alarm and order signals. CONSTITUTION:The light with the polarization fluctuated by a modulation signal is branched by a light branching device 11 at the input of a fiber light amplifier 10 and inputted to a polarization separation board 12 so as to obtain a signal whose light intensity changes according to the fluctuation of polarization. It is converted into an electric signal by a light receiving device 13, demodulated by a demodulator 14, and inputted to an information processing section 15, then allocated to the time slot(TS) in the area allocated to the fiber light amplifier repeater at the front stage of the frame having the areas allocated as many as the fiber light amplifier repeaters. The signal of the self fiber light amplifier repeater is allocated to the TS in the area allocated to the self fiber light amplifier repeater, and the output is inputted to a modulator 16. It is modulated by the modulation frequency different for each fiber light amplifier repeater, and the modulated signal is added to a fiber pressure device 17 of the output of a fiber light amplifier device 10 to fluctuate the polarization state by the modulated signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber optic amplification repeater for use in optical communication systems and the like, capable of transferring alarm signals and meeting signals.

In recent years, attention has been paid to a fiber optical amplifier using an optical fiber in which a rare earth element such as Nd ³⁺ (neodymium) or Er ³⁺ (erbium) is added to the core of an optical fiber as an amplification medium. In particular, Er ³⁺ doped optical fiber has a laser transition frequency in the wavelength range of 1.55 μm, so optical amplification is possible in this wavelength range, and it is expected that the system will have higher functionality and higher performance when applied to optical communication systems. I can.

Optical amplifier repeaters, optical preamplifiers, optical booster amplifiers, and the like are conceivable as application forms of the fiber optical amplifier to the optical communication system. However, transfer of an alarm signal and a meeting signal using the fiber optical amplifier is possible. It is desired to provide a fiber optic amplification repeater that can be used.

[0004]

2. Description of the Related Art FIG. 7 is a block diagram of a conventional optical repeater for relaying by electrical conversion, and FIG. 8 is a diagram showing a conventional fiber optical amplifier.

In the frame format of the optical repeater shown in FIG. 7, as shown in FIG.
It is mapped in rows and 270 × N byte columns, and an alarm signal and a meeting signal of the repeater are placed in the relay section overhead (R-SOH) portion.

In the optical repeater of FIG. 7, the optical-electrical converter 40 converts the signal into an electric signal, the frame synchronization unit 41 synchronizes the frame, the descrambler 42 descrambles the signal, and the relay section overhead processing unit 43, If it is necessary to rewrite the alarm signal and the meeting signal portion in the relay section overhead terminal portion 44, the rewriting scrambler 45 scrambles the signal and the electro-optical converter 46 converts the signal into an optical signal for output.

In the fiber optical amplifier, as shown in FIG. 8, a rare earth-doped optical fiber is wound around a bobbin 51, and pumping light is input from the optical coupler 50 on the input side to amplify the light for a short time and convert it into an electric signal. Therefore, the repeater can be simplified and the reliability can be improved.

[0008]

However, when the fiber optical amplifier is used as a repeater, since it is not converted into an electric signal, the alarm signal and the meeting signal cannot be transferred like the optical repeater shown in FIG. Therefore, when the optical fiber is cut, it is not possible to specify where it is cut and a meeting signal channel must be provided separately.

An object of the present invention is to provide a fiber optic amplification repeater using a fiber optic amplifier capable of transmitting an alarm signal and a meeting signal.

[0010]

FIG. 1 is a block diagram showing the principle of the present invention. As shown in FIG. 1, the light whose polarization state is changed by the modulation signal obtained by modulating the alarm signal and the meeting signal in the fiber optical amplifier repeater in the previous stage is provided with the optical branching device 11 at the input side of the fiber optical amplifier 10. It is provided and branched, part of which is amplified and output by the fiber optical amplifier 10, and the other part of which is input to the polarization separation plate 12 to be separated into one polarized light so as to respond to polarization fluctuation. A signal whose intensity changes is obtained and inputted to the light receiver 13 to be converted into an electric signal, inputted to the demodulator 14 to be demodulated and inputted to the information processing unit 15, and an allocated area corresponding to the number of fiber optical amplifier repeaters. Assigned to the time slot of the area assigned to the preceding fiber optical amplification repeater in the frame having the, and the alarm signal and the meeting signal of the own fiber optical amplification repeater are assigned to the time slot of the area assigned to the own fiber optical amplification repeater. Assigned to Enter to the modulator 16,
Each fiber optical amplification repeater is modulated with a different modulation frequency, and the modulated signal is applied to the fiber pressurizer 17 for applying pressure to the optical fiber, which is provided at the output of the fiber optical amplifier 10, and is modulated by the modulated signal. The configuration is such that the wave state is changed.

[0011]

According to the present invention, the optical branching device 11 and the polarization separating plate 1 are provided.
2, the alarm signal and the meeting signal of the fiber optic amplification repeater in the preceding stage, which are obtained through the photoreceiver 13 and the demodulator 14, are the fibers in the preceding stage in the frame having the allocation regions corresponding to the number of the fiber optic amplification repeaters. Each fiber optical amplifier is assigned to the time slot of the area assigned to the optical amplification repeater, and the alarm signal and the meeting signal of the own fiber optical amplification repeater are assigned to the time slot of the area assigned to the own fiber optical amplification repeater. The alarm signal and the meeting signal of the repeater are assigned to the time slot of each area every time the relay is carried out, and the alarm signal and the meeting signal are allowed to be inserted and extracted by the assigned time slot, and the output is provided by the modulator 16. , A fiber provided at the output of the fiber optical amplifier 10 by modulating with a modulation frequency having a different frequency for each fiber optical amplifier repeater and using the modulated signal. So as to vary the polarization state modulated signal added to the voltage divider 17, and to forward the alarm signals and the meeting signals one after another fiber optical amplifier repeater.

The reason why the polarization state is changed by changing the pressure applied to the optical fiber for relaying the alarm signal and the meeting signal is as follows. FIG. 6 is a diagram showing the polarization stability of light in the laid single mode optical fiber. The P polarization and the S polarization change with a long time constant of several hours, and there is no rapid fluctuation. By intentionally changing the polarization state at a high speed with information, it is possible to add information to the polarization fluctuation and transmit it. Also, if pressure is applied to the fiber, the polarization will change due to its birefringence. Because it causes fluctuations, it is possible to transfer these information by applying a signal obtained by modulating the alarm signal and the meeting signal by the modulator to the fiber pressurizer to change the pressure on the fiber and causing polarization fluctuation. is there.

Even if the polarization component fluctuates as described above, the total optical signal power does not fluctuate (the optical power fluctuates slightly because pressure is applied to the fiber,
It is a negligible amount compared to the extinction ratio of signal light) and does not cause deterioration of signal light.

Further, the reason why the modulation frequency is changed for each fiber optical amplifier repeater is to avoid the influence of the fluctuation of the polarization state in the fiber optical amplifier repeater in the preceding stage.

[0015]

FIG. 2 is a block diagram of a fiber optical amplifier repeater according to an embodiment of the present invention, FIG. 3 is a block diagram of a balanced optical receiver according to an embodiment of the present invention, and FIG. 4 is a drum shape according to an embodiment of the present invention. FIG. 5 is a diagram showing a fiber optical amplifier using a piezoelectric ceramic, and FIG. 5 is a diagram showing a modulation frequency of each repeater according to an embodiment of the present invention.

In FIG. 2, the light receiver 13 is provided with a light input break detection unit 19.
When an optical input interruption is detected, it is input to the information processing section 15, and an optical branching device 21 and a light receiving device 22 are provided at the output, and the light receiving device 22 is also provided.
Is provided with a light output interruption detecting section 23, and when a light output interruption is detected, it is inputted to the information processing section 15, and the drive circuit 25 for driving the pumping light source 26 of the fiber optical amplifier 10 is provided with the bias abnormality detecting section 24 so that the bias abnormality occurs. When information is detected, the information processing unit 15
In addition, the meeting signal is also input to the information processing unit 15.

The modulation frequency of each repeater is shown in FIG.
As shown in (B), if the frequency of the clock of the information processing unit 15 is 2 MHz, the frequency of the repeater 1 is 5 MH.
z, the frequency of the repeater 2 is 10 MHz, and the frequencies f _{1 to} f _n are different at intervals of 5 MHz so as not to be affected by the fluctuation of the polarization state in the fiber optical repeater in the preceding stage as described above. ing.

The frame in the information processing section 15 is shown in FIG.
As shown in FIG. 3, the number of repeaters is as many as possible, and the alarm signal and the meeting signal of each repeater are allocated to the allocated time slot of the allocated area, and the alarm signal and the meeting signal are allocated. Signals can be inserted and extracted by different time slots.

The fiber optical amplifier 10 is the same as that of the prior art example shown in FIG. 8. A driving circuit 25 drives an excitation light source 26 and an optical coupler 28 is added to an Er ³⁺ doped optical fiber 28 to amplify the light. It is the one.

The YIG filter 18 is a filter tuned to the modulation frequency f _n-1 of the preceding fiber optical amplification repeater, and the demodulator 14 is provided with the modulation frequency f _n-1 . A part of the signal, which has been subjected to polarization fluctuation in the fiber optical amplifier repeater in the previous stage, is branched by the optical branching device 11 and is separated into one polarization by the polarization separation plate 12 to correspond to the polarization fluctuation. A signal whose light intensity fluctuates is obtained, converted into an electric signal by the photodetector 13, and Y
The IG filter 18 removes unnecessary frequency bands, and the demodulator 1
4 and demodulated and input to the information processing unit 15 and assigned to the time slot of the area to which the frame is assigned.

The alarm signal and the meeting signal of the own fiber optic amplification repeater are assigned to the time slot of the area assigned to the own fiber optic amplification repeater and input to the modulator 16 at the modulation frequency of frequency f _n . The signal is modulated and input to the drive circuit 20, the pressure of the fiber pressurizer 17 is changed, the polarization of the fiber is changed, and the information processing unit 15 of the next fiber optical amplifier repeater also returns its own fiber optical amplifier repeater. The alarm signal and the meeting signal in (1) are added, and the signals are modulated with different modulation frequencies to cause polarization in the fiber and relayed to be sent to the terminal station.

The terminal station can detect the fiber optical amplification repeater that has issued the alarm signal and the content of the alarm due to the polarization fluctuation according to the timing of the frame shown in FIG. 5 (C). The information processing unit 15 can insert or extract a signal into the time slot of the meeting signal area assigned to each fiber optical amplifier repeater of the frame for the meeting between the repeaters and between the terminal stations. You can do it.

Further, in order to increase the output of the photodetector, as shown in FIG. 3, the P-polarized component and the S-polarized component of the output of the polarization separation plate 12 are respectively received by two photodetectors 13 and 30 and subtracted. Bowl 31
If a balanced photodetector that takes the difference is used, for example, P
If the polarized wave has the phase as shown in FIG. 3A, the S polarized wave has the inverted phase as shown in FIG.
With the output of No. 1, the amplitude can be doubled as shown in FIG. 3C, the gain can be increased by 3 dB, and the receiving sensitivity can be improved, so that the limitation of the repeater interval due to the alarm transfer can be relaxed.

As shown in FIG. 4, the bobbin around which the rare-earth-doped optical fiber is wound is a piezoelectric ceramic bobbin 52.
When the output of the modulator 16 is applied to the piezoelectric ceramic bobbin 52 via the drive circuit 53, the output voltage of the drive circuit 53 changes due to the output change of the modulator 16, and the diameter of the piezoelectric ceramic bobbin 52 changes. Since the fiber wound around 52 expands and contracts to change the polarization state, the polarization can be changed in this way as well. In this case, a fiber pressurizer is not required and the mounting efficiency can be improved.

In the present invention, as an optical communication system in an optical transceiver of a terminal station, not only a system of optical intensity modulation on the transmitting side and direct detection on the receiving side, but also a polarization fluctuation countermeasure such as polarization diversity is taken. If it has been used, it can be applied to a coherent optical communication system.

[0026]

As described in detail above, according to the present invention, a fiber optical amplifier repeater using a fiber optical amplifier capable of transferring an alarm signal and a meeting signal can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of the principle of the present invention,

FIG. 2 is a block diagram of a fiber optic amplification repeater according to an embodiment of the present invention,

FIG. 3 is a block diagram of a balanced type optical receiver according to an embodiment of the present invention,

FIG. 4 is a diagram showing a fiber optical amplifier using a drum-shaped piezoelectric ceramic according to an embodiment of the present invention,

FIG. 5 is a diagram showing a modulation frequency of each repeater according to an embodiment of the present invention,

FIG. 6 is a diagram showing polarization stability of light in an installed single-mode optical fiber,

FIG. 7 is a block diagram of an optical repeater that performs relay by electrical conversion of a conventional example,

FIG. 8 is a diagram showing a conventional fiber optical amplifier.

[Explanation of symbols]

1 to n are fiber optical amplifier repeaters, 10 are fiber optical amplifiers, 11, 21 and 27 are optical branching devices, 12 is a polarization separation plate,
13, 22 and 30 are light receivers, 14 is a demodulator, 15 is an information processing unit, 16 is a modulator, 17 is a fiber pressurizer, 18 is a YIG filter, 19 is an input disconnection detector, 20, 25, 5
3 is a drive circuit, 23 is a light output interruption detector, 24 is a bias abnormality detector, 26 is an excitation light source, 28 is an Er ³⁺ optical fiber, 40 is an optoelectric converter, 41 is a frame synchronization unit, 42
Is a descrambler, 43 is a relay section overhead processing section, 44 is a relay section overhead termination section,
Reference numeral 45 is a scrambler, 46 is an electro-optical converter, 50 is an optical coupler, 51 is a bobbin, and 52 is a piezoelectric ceramic bobbin.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01S 3/07 8934-4M 3/094 3/13 8934-4M H04B 17/00 T 7170-5K 8934 -4MH01S 3 / 094S

Claims (3)

[Claims] 1. The optical branching device (1) outputs the light whose polarization state is changed by a modulation signal obtained by modulating an alarm signal and a meeting signal in a fiber optical amplifier repeater in the preceding stage to an input side of a fiber optical amplifier (10). 11) is provided for branching, part of which is amplified by the fiber optical amplifier (10) and output, and the other part of which is input to the polarization separation plate (12) and separated into one polarization. A signal whose light intensity changes in response to the wave fluctuation is obtained and input to the photodetector (13) to be converted into an electric signal, and the demodulator (1
4), demodulates and inputs to the information processing unit (15),
Allocating to the time slot of the area allocated to the preceding fiber optic amplification repeater in the frame having the allocation area equal to the number of fiber optic amplification repeaters. It is assigned to the time slot in the area assigned to the amplification repeater, the output is input to the modulator (16), modulated at a modulation frequency of a different frequency for each fiber optical amplification repeater, and the modulated signal is output to the fiber optical amplifier. A fiber optic amplification repeater characterized in that a polarization state is changed by a modulated signal in addition to a fiber pressurizer (17) for applying pressure to an optical fiber provided at the output of an amplifier (10). 2. The optical receiver (13) for the output of the polarization separation plate (12) according to claim 1, wherein two P-polarization components and two S-polarization components of the output of the polarization separation plate (12) are provided. A fiber optic amplification repeater characterized in that it is a balanced type light receiver that receives light at the light receiver and detects the difference. 3. Fiber pressurizer (17) according to claim 1.
Instead of changing the polarization state of the fiber with the modulated signal by adding the output of the modulator (16) to the, the bobbin around which the rare earth-doped optical fiber of the fiber optical amplifier (10) is wound is a piezoelectric ceramic bobbin, and the modulator (16) The optical fiber repeater is characterized in that the polarization state of the fiber is changed by a modulated signal by applying the output of the above to the piezoelectric ceramic bobbin.