JP2004282690A - Wavelength selection module and optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the number of filters to be used when using a wavelength selection module for an apparatus. <P>SOLUTION: The wavelength selection module is provided with a wavelength selection part for inputting light with light of a plurality of different wavelengths multiplexed thereon, and selectively outputting light of the plurality of wavelengths corresponding to a control signal imparted from the outside, and a demultiplexing means for demultiplexing out the output light of the wavelength selection part for each wavelength. The module is further equipped with a means for inputting the output light of the demultiplexing means and attenuating out light of an unwanted wavelength. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wavelength filter for selecting and outputting light of a specific wavelength from wavelength-multiplexed light, and an optical dropping / inserting device using the same.

  2. Description of the Related Art In a communication system, a demand for an optical communication system capable of long-distance and large-capacity transmission is high in order to construct a large-capacity and flexible network. Wavelength-division multiplexing (WDM) communication is widely used as a method for achieving long-distance and large-capacity transmission. WDM communication uses the broadband and large capacity of optical fiber, and research on network construction using WDM communication is under way.

  In order to build a flexible network with an optical communication system, the function of passing, dropping, and inserting signal light at each point on the network, the optical routing function of selecting the transmission destination for each signal light, and the clock connect function Is required. Among them, an optical add / drop multiplexing (OADM) device has been researched and developed as a means for realizing the function of passing, dropping, and inserting an optical signal. Known OADM devices include a fixed-wavelength OADM device capable of dropping / adding only an optical signal of a fixed wavelength and an OADM device of an arbitrary wavelength type capable of dropping / adding an optical signal of an arbitrary wavelength. I have.

On the other hand, an acousto-optic tunable filter (AOTF: Acousto-Optic Tunable Filter) is a filter for selecting a wavelength using an acousto-optic effect, and has a wavelength corresponding to a radio frequency (RF) signal applied from the outside. Can be selected. Unlike a fiber grating in which the selected wavelength is fixed, an arbitrary wavelength can be selected by changing the frequency of the RF signal. In addition, it has features such as a wide selection wavelength range (80 nm or more), fast tuning speed (10 μs or less), and simultaneous selection of a plurality of wavelengths. Further, since it is also a variable wavelength selection filter, it can be used as a variable wavelength selection filter in a tributary station which is a station for dropping / adding an optical signal between terminal stations. For these reasons, OADM devices using AOTF have been researched and developed. (For example, see Patent Document 1)
The AOTF is an optical element using the acousto-optic effect shown in FIG. 18, and selects a wavelength using mode conversion due to interaction between a surface acoustic wave (SAW) and light. In FIG. 18, AOTFs are formed on a substrate 26A having birefringence and an acousto-optic effect, and have optical waveguides 24A to 24B, PBSs (Polarized Beam Splitters) 23A to 23B, SAW waveguides 22A, and combs. It comprises an electrode (IDT; Inter Digit Transducer) 21A and absorbers 25A to 25B.

As the substrate 26A, LiNbO ₃ having birefringence and an acousto-optic effect is used, and optical waveguides 24A to 24B and PBSs 23A to 23B are formed by diffusing Ti or the like. The optical waveguides 24A and 24B intersect at two locations, and waveguide-type PBSs 23A to 23B are provided at the intersections. The PBSs 23A and 23B are polarization splitters that change the traveling direction of light based on the polarization of the light of the incident optical waveguide.

  The SAW waveguide 22A is a waveguide through which the SAW generated by the IDT 21A propagates, and the SAW interacts with light at a portion where the SAW intersects the optical waveguides 24A and 24B. The IDT 21A is an electrode that generates a SAW based on the RF signal applied from the external RF signal generator 2A. In a region where the SAW waveguide and the optical waveguide intersect, the refractive indexes of the optical waveguides 24A and 24B change periodically according to the wavelength of the SAW. As a result, of the light propagating through the optical waveguides 24A and 24B, the polarization plane of light having a specific wavelength, which interacts with the periodic change of the refractive index of the optical waveguide due to the SAW, is rotated, and the TE light is converted into the TM light. At the same time, the mode of the TM light is switched to the TE light. The amount of rotation of the polarization plane of light due to the interaction with the SAW is proportional to the length of the interaction and the strength of the RF signal applied to the IDT to generate the SAW. Therefore, by selecting the operation length and the RF signal intensity, it is possible to control the wavelength of light for mode conversion by SAW.

  In the configuration where the optical waveguide and the SAW waveguide intersect as shown in FIG. 18, the SAW waveguide is formed by forming a metal film. When using AOTF to select light in the C band (1.55 μm band; about 1.53 μm to about 1.56 μm) or L band (1.58 μm band; about 1.57 μm to about 1.61 μm), which is the wavelength band used in optical communication The frequency of the applied RF signal is 170 MHz to 180 MHz. Also, absorbers 25A and 25B are provided so that the SAW does not propagate to other than the SAW waveguide 22A.

Here, a case is considered in which light of wavelengths λ ₁ , λ ₂ , and λ ₃ is input to the AOTF shown in FIG. 18, and only light of wavelength λ ₁ is selected and output by an external RF signal. The light of wavelengths λ ₁ , λ ₂ , λ ₃ incident on the input (IN) port is split into TE light and TM light by the PBS 23A, and the TM light of wavelengths λ ₁ , λ ₂ , λ ₃ propagates through the optical waveguide 24B. Then, the TE lights having the wavelengths λ ₁ , λ ₂ , and λ ₃ propagate through the optical waveguide 24A. Wavelength lambda ₁ of the light, the RF signal of the selected frequency and intensity as the mode conversion by the interaction of the SAW and light, by RF signal generating section 2A is applied to IDT21A, the wavelength lambda ₁ light is mode conversion, the TM light and the wavelength lambda ₂ wavelength lambda ₁ to PBS23B from the optical waveguide 24A, the incident lambda ₃ of the TE light, the PBS23B from the optical waveguide 24B wavelength lambda _2, lambda ₃ of the TM light and the wavelength lambda ₁ TE light is incident.

By the PBS 23B, the light incident from the optical waveguide 24A outputs the TE light of wavelengths λ ₂ and λ _{3 to} the transmission (THRU) port and the TM light of wavelength λ _{1 to} the branch (DROP) port. The light incident from the optical waveguide 24B outputs TM light of wavelengths λ ₂ and λ _{3 to} the transmission (THRU) port and TE light of wavelength λ _{1 to} the branch (DROP) port. Therefore, the TE light and TM light of wavelengths λ ₂ and λ ₃ are output to the transmission (THRU) port, and the TE light and TM light of wavelength λ ₁ are output to the drop (DROP) port. The light of the wavelength selected by the signal generator is output to the drop (DROP) port, and the light of the other wavelengths is output to the transmission (THRU) port.

As described above, the AOTF can select and branch only light having a wavelength corresponding to the frequency of an RF signal, and further change the wavelength of the selected light by changing the frequency of the RF signal. Can be. The light output from the transmission (THRU) port is converted from the light (wavelengths λ ₁ , λ ₂ , λ ₃ ) input from the input (IN) port to the wavelength (λ ₁ ) corresponding to the frequency of the RF signal. Since only light is removed (wavelengths λ ₂ and λ ₃ ), the AOTF can be used as a filter having a rejection function for preventing light of a specific wavelength from being output.

When light of wavelengths λ ₄ , λ ₅ , and λ ₆ is input to the insertion (ADD) port and an RF signal corresponding to wavelength λ ₄ is applied to IDT 21A, the wavelength λ ₄ is similarly set as described above. Light is output to the transmission (THRU) port, and light of wavelengths λ ₅ and λ ₆ is output to the branch (DROP) port. Therefore, when light is input to the AOTF insertion (ADD) port, light of a wavelength corresponding to the frequency of the RF signal applied to the IDT 21A is output to the transmission (THRU) port, and light of other wavelengths is branched. (
DROP) port.

  AOTF can change the wavelength of the light to be selected by changing the frequency of the applied RF signal. However, the temperature characteristic that the selected wavelength shifts by 100GHz (approximately 0.8nm in wavelength conversion) by a temperature change of 1 ℃. have.

On the other hand, the wavelength interval of the WDM signal light is specified, for example, as 0.8 nm by the ITU-T G.692 recommendation, and if the frequency of the RF signal applied to the AOTF is not changed, a different signal due to a temperature change of the AOTF. You will choose light. In order to use AOTF in WDM communication, research and development are also being conducted on a control method for the temperature change of AOTF. (For example, see Patent Document 1)
FIG. 19 shows an OADM device according to a conventional technique using a wavelength selection module using AOTF. The OADM device in FIG. 19 includes optical couplers 9A to 9C, an optical amplifier 11A, an optical amplifier 11B, a variable wavelength selection module 20A to 20D, a transponder 15A, an optical attenuator (ATT) unit 12A, a band rejection optical filter (BRF; Band). Rejection Filter) 16A. The transponder unit 15A includes an optical receiving unit 13A and an optical transmitting unit 14A.

  The variable wavelength selection modules 20A to 20D are wavelength selection modules using AOTF, and select and output light of a specific wavelength from input light. The BRF 16A uses the rejection function of the AOTF, and outputs the light corresponding to the frequency of the applied RF signal from the light input from the insertion (ADD) port to the transmission (THRU) port. . Further, of the light input from the input (IN) port, the light corresponding to the frequency of the applied RF signal is output to the branch (DROP) port and not output to the transmission (THRU) port.

  The transponder unit 15A receives the input signal light by the optical receiving unit 13A, converts the signal light into an electric signal, and then inserts the signal light into the WDM signal light by the optical transmitting unit 14A and multiplexes the optical signal. Is sent out.

In the OADM device shown in FIG. 19, light of wavelengths λ _{1 to} λ ₄ is split into light of a single wavelength from the input WDM signal light and output, and the inserted light is wavelength λ ₅ to λ _8. A case where the light is multiplexed with the WDM signal light and output is described.

The WDM signal light input to the input (IN) port of the OADM device is split by the coupler 9A and input to the BRF 16A and the optical amplifier 11A. The light input to the optical amplifier 11A is amplified, demultiplexed by the coupler 9B, and input to the variable wavelength selection modules 20A to 20D. The tunable wavelength selection modules 20A to 20D respectively select light of wavelengths λ ₁ , λ ₂ , λ ₃ , and λ ₄ and output the light of a single wavelength to the branch optical port of the OADM device.

On the other hand, the light input to the insertion port of the OADM device changes the wavelength of the signal light by the transponder unit 15A and outputs it as light of wavelengths λ ₅ , λ ₆ , λ ₇ and λ ₈ . The outputted light of wavelengths λ _{5 to} λ ₈ is amplified by the optical amplifier 11B, the light intensity is adjusted by the ATT unit 12A, multiplexed by the coupler 9C, and input to the insertion (ADD) port of the BRF 16A. I do.

The WDM signal light split by the coupler 9A is input to the input (IN) port of the BRF 16A, and the light of wavelengths λ _{5 to} λ ₈ multiplexed by the coupler 9C is input to the insertion (ADD) port of the BRF 16A. Is done. To output the light input to the insertion (ADD) port to the transmission (THRU) port, an RF signal having a frequency corresponding to wavelengths λ _{5 to} λ ₈ is applied to the BRF 16A. ) Of the WDM signal light input to the port, the light of wavelengths λ _{5 to} λ ₈ is output to the drop (DROP) port, so the light excluding wavelengths λ _{5 to} λ ₈ is output to the transmission (THRU) port. Is done.

Thus, the transmission (THRU) ports, of the WDM signal light input to the OADM device, a light excluding the light of the wavelength lambda ₅ to [lambda] _8, the wavelength input to the insertion of BRF16A (ADD) port lambda ₅ that light to [lambda] ₈ is wavelength-multiplexed is output.

  In the current network of the optical transmission system, communication is performed between a transmitting terminal station and a receiving terminal station by a stream system for continuously transmitting signal light. In optical transmission systems, technology that relays data as it is, without converting optical signals to electrical signals, has been put to practical use. It is possible to reduce costs by reducing optical-electrical and electrical-optical converters, and to switch signal light itself. Thus, a repeater independent of a bit rate and a protocol has been realized. In order to realize a flexible network configuration, development of a relay node that can switch a transmission path for each signal light wavelength is also being performed.

  On the other hand, as in the current stream system, instead of performing signal transmission after establishing communication between terminal stations, development of an optical burst switching system in which a relay node is switched for each piece of data is being advanced. FIG. 18A schematically shows the configuration of an optical network for performing communication by the optical burst switching method, and FIG. 18B shows the structure of a signal transmitted to a control channel and a data channel in the optical burst switching method. It is a diagram schematically showing a change with respect to time.

  In FIG. 18A, an optical burst switching network 70 that performs communication by the optical burst switching method is connected to the optical burst switching network 70 and the access network 71, and is transmitted through a control channel and an edge node 73 that transmits burst data. It is composed of a relay node that switches the transmission path of burst data in accordance with the information of the control packet, and the edge node and the relay node, or between the relay nodes, are connected by N data channels composed of WDM signal light.

  FIG. 18B shows a time relationship between a control packet and burst data in communication using the optical burst switching method. In communication using the optical burst switching method, a control packet is transmitted from the edge node 73 to a control channel prior to data. The control packet is converted into electricity at the relay node 74 and processed, and the data channel is switched at the relay node 74 based on the content of the control packet. After transmission of the control packet, burst data is transmitted at an offset time T1, and the relay node switched based on the content of the control packet is relayed as light and transmitted to the target edge node.

  Since a data channel of a specific wavelength is allocated to burst data transmitted in the optical burst switching method for a time required for transmitting the burst data, the utilization efficiency of the optical network can be improved.

The switching time T2 of the data channel in the optical burst switching method is a time of millisecond order or less, and the switching time of the relay node shown in FIG. .
JP-A-2000-241782

  When a variable wavelength device using AOTF is used in stream communication, an RF signal is adjusted so that a target wavelength is selected before communication starts. After the start of communication, by performing tracking (tracking) adjustment to the input signal light of the target wavelength, it is possible to cope with a change in the relationship between the RF signal frequency and the selected wavelength due to a temperature change or the like. It is enough to consider only the previous adjustment.

  On the other hand, in the optical burst switching method, since a data channel of a certain wavelength is allocated only for the time required for transmitting burst data, it is not sufficient to correct the relationship between the RF signal frequency and the selected wavelength by tracking, and every time the wavelength is switched. The relationship between the RF signal frequency and the selected wavelength must be correctly recognized.

  Also, in an OADM device using a variable wavelength selection device such as AOTF, a single wavelength branch light can be obtained in a wide range by changing the selection light wavelength of the variable wavelength selection device. When the number of wavelengths to be added increases and the number of signals to be dropped / added at each point in the network increases, it is necessary to arrange variable wavelength selection devices such as AOTFs by the number of signals to be dropped / inserted.

  For this reason, in the OADM apparatus, in order to increase the number of signal lights to be dropped / inserted, it is necessary to provide a variable wavelength selection device corresponding to the number of dropped / inserted signals, which increases the manufacturing cost.

  The present invention solves the above-mentioned problems, and a wavelength selection module according to a first invention is provided with a plurality of lights multiplexed with lights of a plurality of different wavelengths, the plurality of lights being multiplexed according to a control signal given from outside. A wavelength selector for selecting and outputting the light of the wavelengths described above, and a demultiplexer for demultiplexing and outputting the output light of the wavelength selector for each wavelength.

  A wavelength selecting module according to a second aspect of the present invention is the wavelength selecting module according to the first aspect of the present invention, further comprising means for inputting the output light of the demultiplexing means, and attenuating and outputting light of an unnecessary wavelength. Features.

  A wavelength selection module according to a third aspect of the present invention includes a wavelength selection unit that inputs light of a plurality of different wavelengths, selects and outputs light of a plurality of wavelengths according to a control signal supplied from the outside, and an output of the wavelength selection unit. To a first and a second light, a first filter for inputting the second light and selectively transmitting a light of a specific wavelength, and a control signal and a first filter for the first filter. A control unit that adjusts a relationship between a control signal given to the wavelength selection unit and the selected wavelength based on an output and a transmission wavelength of the filter.

  A wavelength selection module according to a fourth aspect of the present invention includes: a reference light source having a constant output wavelength; multiplexing means for multiplexing input light including light of a plurality of different wavelengths and output light of the reference light source; Wavelength selecting section for inputting the output light and selecting and outputting light of a plurality of wavelengths according to a control signal given from the outside, and branching means for branching the output of the wavelength selecting section into first and second lights A first filter for inputting the second light and selectively transmitting light having an output light wavelength of the reference light source; and a control signal, an output of the first filter, and a wavelength of the reference light source. And a controller for adjusting the relationship between the control signal given to the wavelength selector and the selected wavelength.

  A wavelength selection module according to a fifth aspect of the present invention includes a first and a second reference light source having a constant output wavelength, an input light including a plurality of light of different wavelengths, and an output light of the first and the second reference light source. Multiplexing means for multiplexing, a wavelength selecting section for inputting output light of the multiplexing means, selecting and outputting light of a plurality of wavelengths according to a control signal given from the outside, and an output of the wavelength selecting section. Branching means for branching into first to third light; a first filter for inputting the second light and selectively transmitting light having an output light wavelength of the first reference light source; A second filter for inputting light and selectively transmitting light having an output light wavelength of the second reference light source, and a relationship between the control signal, an output of the first filter, and a wavelength of the first reference light source; And the control signal, the output of the second filter, and the wavelength of the second reference light source Based on the relationship, characterized by comprising a control unit for adjusting the relationship between the selected wavelength and a control signal applied to the wavelength selection unit.

  A wavelength selection module according to a sixth aspect of the present invention is the wavelength selection module according to the third to fifth aspects, wherein the control unit controls the light selectively transmitted by the first or second filter to the wavelength selection unit. The control signal is controlled so as to continuously select the control signal.

  A wavelength selection module according to a seventh aspect is the wavelength selection module according to the third to fifth aspects, wherein the control unit is configured to control the control corresponding to light selectively transmitted by the first or second filter. By suppressing the output of the signal, the output of the wavelength of the light selectively transmitted by the first or second filter to the first light is suppressed.

  The wavelength selection module according to an eighth aspect is the wavelength selection module according to the third to fifth aspects, wherein the first light is input and the control unit is selectively transmitted by the first or second filter. And a third filter for attenuating the wavelength of the light.

  Further, by applying the variable wavelength selection module according to the present invention to an optical add / drop device, it is possible to increase the number of signal light wavelengths that can be dropped / added at the same time without greatly increasing the number of wavelength selection units used. Can be.

  According to the wavelength selection module of the present invention, a wavelength selection module configured to selectively demultiplex and output two or more different wavelengths of light from a plurality of wavelength-multiplexed lights of different wavelengths is configured.

  Also, by applying the wavelength selection module according to the present invention to an optical add / drop device, it is possible to increase the number of signal light wavelengths that can be dropped / added at the same time without greatly increasing the number of wavelength selection units used. it can.

  Further, according to the wavelength selection module of the present invention, the relationship between the control signal and the selected wavelength can be adjusted while the light of the specific wavelength is being selected. Even in the case where switching is frequently performed and a time for adjusting the relationship between the control signal and the selected wavelength cannot be provided separately, the signal light of the target wavelength can be selected.

[A] First Embodiment Hereinafter, an embodiment of the present invention will be described. The wavelength selection module according to the first embodiment of the present invention shown in FIG. 1 includes a wavelength selection unit 1A, a control unit (CTRL) 3A, RF signal generation units (RF OSC) 2A to 2B, and a mixing unit (Mixer) 7A. , A monitor section (MON) 4A, a coupler 9A, a wavelength separation filter 8A as demultiplexing means, and optical filters 5A to 5B.

  The wavelength selection unit 1A is a wavelength selection element that can select and output light of a plurality of wavelengths by an external control signal from input light in which light of a plurality of wavelengths is multiplexed, and use an element such as an AOTF. it can.

  As shown in FIG. 18, the AOTF selects light having a wavelength corresponding to the frequency of the RF signal applied to the IDT 21A through the RF signal input port from the light input to the input (IN) port, and branches the light (DROP). ) Output from the port. When an RF signal of a plurality of frequencies is input to the RF signal input port, light having a wavelength corresponding to each RF signal frequency is selected and output.

  The RF signal generators 2A and 2B generate an RF signal corresponding to a target selected wavelength under the control of the controller 3A. FIGS. 13A and 13B show an example of the configuration of an RF signal generator, which amplifies, filters, and outputs an RF signal generated by a digital direct synthesis oscillator (DDS; Direct Digital Synthesizer). As a result, an RF signal of a target frequency is output.

  The coupler 9A splits a part of the light output from the wavelength selector 1A to the monitor 4A, and outputs the remaining light to the wavelength separation filter 8A.

  The wavelength separation filter 8A is a filter that separates the output from the coupler 9A into an optical filter 5A and an optical filter 5B. The wavelength separation filter 8A according to the first embodiment separates the light in the C band wavelength region from the light output from the coupler 9A into the optical filter 5A and the light in the L band wavelength region into the optical filter 5B. And output.

  As the wavelength separation filter 8A, a low-pass filter or a high-pass filter that can divide a large band wavelength can be used. If light having a transmission wavelength and a reflection wavelength of the low-pass filter or the high-pass filter is used, the wavelength band is divided into two, It can be a separate output. The configuration of a filter that divides a wavelength band into two is simpler than the configuration of a filter that extracts a specific wavelength, and is lower in cost.

  The optical filter 5A is an optical filter that transmits only the light in the C band region and attenuates the light other than the C band region of the light split by the wavelength separation filter 8A, so that the C band selected by the wavelength selector 1A is used. Is output to the output (OUT) port 1 of the optical filter.

  Similarly, the optical filter 5B is an optical filter that transmits only light in the L-band region, and attenuates light other than the L-band region of the light split by the wavelength separation filter 8A. Only the L band light is output to the output (OUT) port 2 of the optical filter.

  Since the optical filters 5A and 5B are filters that supplement the demultiplexing operation of the wavelength separation filter 8A, inexpensive filters such as low-pass filters and high-pass filters having a wide transmission band can be used.

  That is, by combining the inexpensive wavelength separation filter 8A with the inexpensive optical filters 5A and 5B, the light of a plurality of wavelengths selected by the wavelength selector 1A can be output (OUT) in the same manner as when a single wavelength is selected. ) Can be output from ports 1 and 2.

  The monitor unit 4A inputs the light demultiplexed by the coupler 9A and outputs the intensity as a digital signal to the control unit 3A. FIG. 16A shows an example of the monitor unit 4A, in which input light is received by a photodiode (PD) 55A, converted into an electric signal, and then amplified at a Log level by a current-voltage conversion Log amplifier 56A. I do. The output of the current-voltage conversion Log amplifier 56A is amplified by a non-inverting amplifier 57A, filtered by a low-pass filter (LPF) 58A, converted to a digital signal by an analog-digital converter (ADC) 31A, and output. Is done. The monitor unit 4A can output light having a wide dynamic range as a digital signal by using the current-voltage conversion Log amplifier 56A. Therefore, the intensity of the light that has been demultiplexed and input by the wavelength separation filter 8A can be output. Irrespective of the magnitude of the input light intensity, it can be output as a digital signal associated with the input light intensity.

  The control unit 3A receives the digital signal output from the monitor unit and outputs a control signal that defines the frequency, amplitude, and phase generated from the RF signal generation units 2A and 2B. As shown in FIG. 16B, the control unit 3A includes an MPU unit 27A, a ROM unit 28A, a RAM unit 29A, and an EEPROM unit 30A. The ROM unit 27A is used as a storage unit for storing a program for operating the control unit, the RAM unit 29A is used as a temporary data storage unit, and the EEPROM unit 30A is used as a unit for storing setting information.

(Configuration 1 of RF signal generator)
FIG. 13A shows a configuration of an RF signal generating unit that generates an RF signal corresponding to a selected wavelength by a multiplier, which is described in the specification of Japanese Patent Application No. 2000-149555. The RF signal generator shown in FIG. 13A includes a DDS 51A, band pass filters (BPF) 52A to 52C, high frequency amplifiers (RF AMPs) 53A to 53C, and a multiplier 54A.

  The DDS 51A outputs an RF signal (hereinafter referred to as a sine wave signal or a cosine wave signal) of a frequency (85 MHz to 90 MHz) designated by an external control signal and having a phase shifted by π / 2 from each other. The sine wave signal and the cosine wave signal output from the DDS 51A have unnecessary wave components removed by the band-pass filters 52A or 52B, respectively, are amplified by the high-frequency amplifier 53A or 53B, and input to the multiplier 54A.

  Since the sine wave signal and the cosine wave signal are out of phase with each other by π / 2, they are multiplied by the multiplier 54A and output at a double frequency (170 MHz to 180 MHz). The RF signal output by the multiplier 54A is subjected to removal of unnecessary wave components by a band-pass filter 52C, amplified by a high-frequency amplifier 53C, and output as an output of an RF signal generator.

  In the RF signal generation unit shown in FIG. 13A, even if the frequency of the RF signal that can be directly output by the DDS does not reach the frequency (170 MHz to 180 MHz) corresponding to the wavelength selected by the wavelength selection unit, the multiplication is performed. The frequency (170 MHz to 180 MHz) corresponding to the wavelength selected by the wavelength selection unit is output by using the wavelength selector.

(DDS configuration 1)
FIG. 14 shows the configuration of the DDS 51A used in FIG. 13A. The DDS shown in FIG. 14 includes a reference clock multiplier 65A, a phase calculator 61A, a sine wave / amplitude converter 62A, a cosine wave / It comprises an amplitude converter 62B, digital multipliers 66A to 66B, DA converters (DACs) 63A to 63B, a frequency / phase / amplitude program register 64A, and a data input register 64B.

  In FIG. 14, frequency / phase / amplitude setting information from an external control device is input to a data input register 64B as a write timing signal, a parallel address signal, and a parallel data signal. The input information is input from the data input register 64B to the frequency / phase / amplitude program register 64A. The phase setting information for the frequency is input to the phase calculator 61A, and the amplitude setting information is input to the digital multipliers 66A and 66B. Is entered.

  The reference clock multiplier 65A generates a reference clock signal based on a reference clock signal from outside the DDS 51A, and adds the reference clock signal to the phase calculator 61A, the digital multipliers 66A to 66B, and the DA converters 63A to 63B. The phase calculator 61A inputs the phase information of 0 to 2π to the sine wave / amplitude converter 62A and the cosine wave / amplitude converter 62B for each reference time based on the reference clock signal. The sine wave / amplitude converter 62A converts the data into amplitude data using a sine wave look-up table held in the sine wave / amplitude converter 62A, and the cosine wave / amplitude converter 62B outputs a cosine wave look-up held in the cosine wave / amplitude converter 62B. It is converted into amplitude data by the up table. Thereby, the digital signal of the amplitude information of the sine wave from the sine wave / amplitude converter 62A and the digital signal of the amplitude information of the cosine wave from the cosine wave / amplitude converter 62B according to the phase information of 0 to 2π output from the phase calculator. Are respectively output.

  The digital multiplier 66A multiplies the digital signal of the sine wave amplitude information input from the sine wave / amplitude converter 62A by the amplitude value according to the amplitude setting information input from the frequency / phase / amplitude program register 64A, and Output to converter 63A. Similarly, the digital multiplier 66B multiplies the digital signal of the cosine wave amplitude information input from the cosine wave / amplitude converter 62B by the amplitude value based on the amplitude setting information input from the frequency / phase / amplitude program register 64A. Then, the data is output to the DA converter 63B.

  The DA converters 63A and 63B convert the digital signals output from the digital multipliers 66A and 66B into analog signals, and output them as sine wave signals and cosine wave signals, respectively.

  In the configuration of the DDS shown in FIG. 14, the amplitudes of the sine wave signal and the cosine wave signal to be output are determined based on the amplitude information of the sine wave and cosine wave digital signals and the amplitude setting information of the frequency / phase / amplitude program register. Therefore, it is possible to control to a signal output of a desired amplitude value without providing a variable attenuator.

  When the output frequency of the DDS is changed, the phase setting information about the frequency applied to the phase calculator 61A is changed by the parallel data signal, and the frequency of the output signal is changed. Quick in comparison. When DDS is used for the RF signal source of the wavelength selection unit, the time required for switching the selection frequency of the wavelength selection unit can be, for example, about 1 μs, which is compared with the case where the PLL is used for the RF signal source of the wavelength selection unit. Thus, it is about 1000 times faster.

(Configuration 2 of RF signal generator)
FIG. 13B shows another configuration of the RF signal generator that generates an RF signal corresponding to the selected wavelength by the multiplier. The RF signal generator shown in FIG. 13B includes a DDS 51B, a band pass filter (BPF) 52D, and a high frequency amplifier (RF AMP) 53D.

  The DDS 51B outputs a frequency (170 MHz to 180 MHz) specified by an external control signal. The RF signal output from the DDS 51B is subjected to removal of unnecessary wave components by a band-pass filter 52D, amplified by a high-frequency amplifier 53D, and output as an output of an RF signal generator.

  In the RF signal generator shown in FIG. 13B, since the DDS can directly output the frequency (170 MHz to 180 MHz) corresponding to the wavelength selected by the wavelength selector, the frequency range in which the DDS can directly output is narrow. The configuration is simpler than in the case of (1).

(DDS configuration 2)
FIG. 15 is an explanatory diagram of the DDS 51B used in FIG. 13B. The reference clock multiplier 65A, the phase calculator 61A, the sine wave / amplitude converter 62A, the digital multiplier 66A, the DA converter (DAC) 63A, the frequency -It is composed of a phase / amplitude program register 64A and a data input register 64B.

  The DDS shown in FIG. 15 is basically the same as the configuration of the DDS shown in FIG. 14, but the phase calculator 61A, the digital multiplier 66A, and the DA converter 63A are faster than the DDS shown in FIG. FIG. 14 shows that the frequency (170 MHz to 180 MHz) corresponding to the wavelength selected by the wavelength selector can be directly output by setting the reference clock signal at a high speed and increasing the operation speed. Different from DDS.

  In FIG. 15, frequency / phase / amplitude setting information from an external control device is input to a data input register 64B as a write timing signal, a parallel address signal, and a parallel data signal. The respective information is input from the data input register 64B to the frequency / phase / amplitude program register 64A, the phase setting information on the frequency is input to the phase calculator 61A, and the amplitude setting information is input to the digital multiplier 66A.

  The reference clock multiplier 65A generates a reference clock signal based on a reference clock signal from outside the DDS 51B, and applies the reference clock signal to the phase calculator 61A, the digital multiplier 66A, and the DA converter 63A. The phase calculator 61A inputs the phase information of 0 to 2π to the sine wave / amplitude converter 62A for each reference time according to the reference clock signal. The sine wave / amplitude converter 62A converts the data into amplitude data using a sine wave lookup table held in the sine wave / amplitude converter 62A. Thereby, a digital signal of the amplitude information of the sine wave is output from the sine wave / amplitude converter 62A according to the phase information of 0 to 2π output from the phase calculator.

  The digital multiplier 66A multiplies the digital signal of the sine wave amplitude information input from the sine wave / amplitude converter 62A by the amplitude value according to the amplitude setting information input from the frequency / phase / amplitude program register 64A, and Output to converter 63A. The DA converter 63A converts the digital signal output from the digital multiplier 66A into an analog signal, and outputs it as a sine wave signal.

  In the configuration of the DDS shown in FIG. 15, since the amplitude of the sine wave signal to be output is determined based on the amplitude information of the sine wave digital signal and the amplitude setting information of the frequency / phase / amplitude program register, a variable attenuator is provided. Thus, it is possible to control to a signal output of a desired amplitude value.

  Further, since the DDS can directly output a frequency (170 MHz to 180 MHz) corresponding to the wavelength selected by the wavelength selector, it is not necessary to provide a configuration for multiplying the frequency at the subsequent stage of the DDS, for example, a multiplier or the like. Small size is possible.

  Furthermore, when the output frequency of the DDS is changed, the phase setting information about the frequency applied to the phase calculator 61A is changed by the change of the parallel data signal, and the frequency of the output signal is changed. Fast compared to frequency changes. When DDS is used for the RF signal source of the wavelength selection unit, the time required for switching the selection frequency of the wavelength selection unit can be, for example, about 1 μs, which is compared with the case where the PLL is used for the RF signal source of the wavelength selection unit. Thus, it is about 1000 times faster.

(Wavelength Selection Operation According to First Embodiment)
Next, the operation of the wavelength selection module according to the first embodiment of the present invention will be described.

  FIG. 1 shows a configuration of the wavelength selection module according to the first embodiment. FIGS. 2A to 2D schematically show the spectrum of light in the configuration of each stage of the wavelength selection module according to the first embodiment, with the horizontal axis representing wavelength and the vertical axis representing light intensity. . FIG. 2A shows the spectrum of light input to the input port of the wavelength selector 1A, and FIG. 2B shows the spectrum of light output from the output port of the wavelength selector 1A and input to the wavelength separation filter 8A. 2 (c) shows the spectrum of light output from the wavelength separation filter 8A and input to the optical filter 5A, and FIG. 2 (d) shows the spectrum of light output to the output (OUT) port of the optical filter 5A.

  In FIG. 1, the input WDM signal light is input to an input port of the wavelength selector 1A. As shown in FIG. 2A, the light input to the wavelength selector 1A is light obtained by wavelength-multiplexing C-band and L-band light. RF signals including a plurality of frequencies are input from the RF signal generators 2A and 2B to the RF signal input port of the wavelength selector 1A via the mixer 7A.

  When the AOTF shown in FIG. 18 is used as the wavelength selector 1A, the input port of the wavelength selector 1A corresponds to the input (IN) port of the AOTF, and the output port of the wavelength selector 1A corresponds to the branch (DROP) port of the AOTF. I do. Of the WDM signal light input to the input (IN) port of the AOTF, the light of the wavelength corresponding to the frequency of the applied RF signal is output to the branch (DROP) port by mode conversion, and is output to the other wavelength. Light is output to the transmission (THRU) port. The RF signal output from the mixer 7A to the wavelength selector 1A is output from the RF signal generators 2A and 2B, and its frequency is determined by the controller 3A.

The frequencies of the RF signals output by the RF signal generators 2A and 2B are f ₁ and f ₂ , respectively, and the wavelength of the light to be mode-converted when the RF signals of the frequencies f ₁ and f ₂ are input to the wavelength selector 1A. Are λ ₁ and λ ₂ , respectively, light of wavelengths λ ₁ and λ ₂ is output from the branch (THRU) port of the AOTF that is the wavelength selection unit 1A.

Here, f ₁ and f ₂ are determined so that λ ₁ is in the C band wavelength band and λ ₂ is in the L band wavelength band. Thus, as shown in FIG. 2B, the output light from the branch (DROP) port of the wavelength selector 1A is divided into light (wavelength λ ₁ ) in the C-band wavelength region and L-band wavelength region. Is multiplexed with the light (wavelength λ ₂ ).

Since the wavelength separation filter 8A is a filter that outputs light in the C-band wavelength region to the optical filter 5A and light in the L-band wavelength region to the optical filter 5B, the light of wavelength λ ₁ is output to the optical filter 5A. The light having the wavelength λ ₂ is output to the optical filter 5B. Figure 2 (c) solid line is the spectrum of the light input to the optical filter 5A is output from the wavelength separation filter 8A, the light of the wavelength lambda ₁ in the wavelength region of the C-band, the isolation of a wavelength separation filter 8A not completely Due to this, the light of wavelength λ _{2 in} the L band wavelength region is output from the wavelength separation filter 8A to the optical filter 5A.

The optical filter 5A is an optical bandpass filter that transmits only the light in the C band region, and has the characteristic shown by the dotted line in FIG. 2C. Therefore, the light input to the optical filter 5A from the wavelength separation filter 8A is Filtered according to characteristics. As a result, the output of the optical filter 5A becomes only the light having the wavelength λ ₁ and is output to the output (OUT) port 1 as shown in FIG.

Similarly, the light input from the wavelength separation filter 8A to the optical filter 5B also filtered by characteristic of transmitting only light in L band region of the optical filter 5B, the output of the optical filter 5B becomes only light of the wavelength lambda _2, Output to the output (OUT) port 2.

  The intensity of the light split by the coupler 9A and input to the monitor unit (MON) 4A is output to the control unit 3A as a digital signal as shown in FIG. Thus, the intensity and frequency of the RF signal output from the RF signal generators 2A and 2B can be controlled.

(Selected Wavelength Correction Operation According to First Embodiment)
In the first embodiment, when the temperature of the wavelength selector changes and the relationship between the RF signal frequency and the selected wavelength changes, the output frequency of the RF signal generator 2A or 2B is changed, and the output signal of the monitor 4A is changed. Is used, it is possible to perform correction so that light of a target wavelength can be selected.

  The selected wavelength spectrum of the wavelength selection unit has side lobes above and below the selected wavelength, but the intensity of the side lobe is weaker than the light intensity of the selected wavelength, so the wavelength selection is performed by the voltage value of the ADC 31A output from the monitor unit 4A. It is possible to identify that the wavelength corresponding to the RF signal frequency applied to the unit 1A is the input light wavelength of the wavelength selection unit. When the AOTF is used as the wavelength selection unit, as shown in FIG. 18, when the frequency of the RF signal applied to the IDT 21A is increased, the wavelength of the SAW propagating through the SAW waveguide 22A is shortened. The wavelength of the selected light also becomes shorter.

  The RF signal frequency and the selected wavelength are in an inverse relationship, and for a small decrease in the RF signal frequency, the selected wavelength increases in proportion. Therefore, if the RF signal frequency corresponding to a certain optical wavelength and the rate of change of the optical wavelength with respect to the RF signal frequency are obtained, the RF signal frequency corresponding to an arbitrary optical wavelength can be calculated. Since the rate of change of the optical wavelength with respect to the RF signal frequency hardly changes with temperature, if this value is stored, the RF signal frequency corresponding to a certain optical wavelength can be obtained to respond to light of an arbitrary wavelength. RF signal frequency can be obtained.

  Similarly, if the frequency of the RF signal corresponding to the WDM signal of a certain channel and the RF frequency per WDM signal light channel are obtained, the frequency of the RF signal corresponding to the WDM signal of another channel can be obtained.

  Hereinafter, a method for correcting a change in the relationship between the RF signal frequency and the selected wavelength due to a temperature change or the like in the first embodiment will be described with reference to FIG.

  First, it is assumed that the RF signal applied to the wavelength selection unit 1A is only one frequency. FIG. 3A is a schematic diagram showing the relationship between the WDM signal light and the selected wavelength when decreasing the selected wavelength of the wavelength selector 1A from the longer wavelength side, with the horizontal axis representing the wavelength and the vertical axis representing the light intensity. It is a representation. When the frequency of the RF signal output from the RF signal generation unit 2A is increased in steps of 1 kHz from 170 MHz, the selected wavelength of the wavelength selection unit 1A decreases due to the increase in the frequency of the RF signal. As a result, the selected wavelength of the wavelength selector 1A changes to the shorter wavelength side.

By increasing the frequency of the RF signal and changing the wavelength selected by the wavelength selector to the shorter wavelength side, when the output of the monitor 4A is initially in the input light selection state, the output of the monitor 4A is at the peak output. The frequency of the RF signal applied to the wavelength selector 1A is recorded as the RF frequency f _L corresponding to the longest wavelength. As shown in FIG. 3A, the selected wavelength λ _L corresponding to the RF signal of the frequency f _L is the longest wavelength of the WDM signal light.

  FIG. 3A is a schematic diagram showing the relationship between the WDM signal light and the selected wavelength when decreasing the selected wavelength of the wavelength selector 1A from the longer wavelength side, with the horizontal axis representing the wavelength and the vertical axis representing the light intensity. It is a representation. Next, when the frequency of the RF signal output from the RF signal generation unit 2B is reduced in steps of 1 kHz from 180 MHz, the selected wavelength of the wavelength selection unit 1A increases due to the decrease in the frequency of the RF signal. As shown by the dotted line, the selected wavelength of the wavelength selector 1A changes to the longer wavelength side.

By reducing the frequency of the RF signal and changing the wavelength selected by the wavelength selector to the longer wavelength side, when the output of the monitor 4A is initially in the input light selection state, the output of the monitor 4A is at the peak output. the frequency of the RF signal applied to the wavelength selection unit. 1A, recorded as the corresponding RF frequency f _H to the longest wavelength. As shown in FIG. 3B, the selected wavelength λ _L corresponding to the RF signal of the frequency f _L is the shortest wavelength of the WDM signal light.

Since the RF frequency Δf per WDM signal light channel can be obtained from the difference between f _L and f _H and the number of WDM signals obtained from information of supervisory control light or the like generally used in WDM communication, the shortest wavelength The frequency of the RF signal corresponding to the n-th signal light wavelength is obtained as f _H − (n−1) × Δf. Therefore, even if the relationship between the RF signal frequency and the selected wavelength changes due to the temperature change of the wavelength selector, the correction can be made by using the output of the monitor 4A.

  As described above, according to the first embodiment of the present invention, a wavelength selection module capable of selecting and outputting light of two wavelengths that are not wavelength-multiplexed using one wavelength selection unit is simply configured. can do.

  In addition, using the monitor output, record the RF signal frequency corresponding to the longest wavelength and the shortest wavelength of the WDM signal light, and combine with the number of signals of the WDM signal light obtained from other sources to change the temperature of the wavelength selector, etc. , The change in the relationship between the RF frequency and the selected wavelength can be corrected.

Furthermore, in the case where AOTF is used as the wavelength selection unit, when light of a plurality of wavelengths is selected at the same time, it is necessary to determine the frequency of the RF signal in consideration of the effect of the attraction effect of the simultaneous selection. When the wavelength of the selected light is determined such that λ ₁ is in the wavelength band of the C band and λ ₂ is in the wavelength band of the L band as in the _first embodiment, the two wavelengths are separated from each other. The effects of the effects need not be considered at all.

[B] Second Embodiment FIG. 5 shows a wavelength selection module according to a second embodiment of the present invention. The wavelength selection module according to the second embodiment includes a wavelength selection unit 1A capable of selecting a plurality of wavelengths, a control unit (CTRL) 3A, RF signal generation units (RF OSC) 2A to 2B, a mixing unit (Mixer) 7A, and a monitor. This is a wavelength selection module composed of units (MON) 4A to 4B, optical filters 5C to 5D, and couplers 9A to 9B. The operations of the wavelength selector 1A, the RF signal generators 2A to 2B, and the mixer 7A are the same as in the first embodiment.

  The second embodiment is a wavelength selection module that uses AOTF as the wavelength selection unit and corrects the relationship between the frequency of the RF signal applied to the AOTF and the AOTF selection wavelength using the monitoring control light.

  The optical filter 5C is a filter that attenuates the wavelength of the monitor control light, and performs monitor control so that the output of the wavelength selection module output through the coupler 9B does not include the monitor control light among the light branched by the coupler 9A. Blocks light wavelengths and transmits light of other wavelengths.

  On the other hand, the optical filter 5D is a filter that selectively transmits light of the monitor control light wavelength from the light branched from the coupler 9A, and the light after the filter is input to the monitor 4A. To selectively transmit the wavelength of the supervisory control light means that only the wavelength of the supervisory control light out of the light output from the wavelength selector 1A is transmitted, for example, the wavelength of the wavelength-multiplexed signal light. If the wavelength of the supervisory control light is shorter than that, a low-pass filter can be used. If the supervisory control light exists between the wavelengths of the wavelength-multiplexed signal light, a band-pass filter can be used.

  The monitor unit 4A receives the light that has been demultiplexed by the coupler 9A and filtered by the filter 5D, and outputs the intensity as a digital signal to the control unit 3A. The configuration of the monitor unit 4A is the same as that of the monitor unit in the first embodiment. A digital signal associated with the input light intensity obtained by the current-voltage conversion Log amplifier having a wide dynamic range is transmitted to the control unit 3A. Output.

  In the second embodiment, since the light of the wavelength corresponding to the applied RF signal frequency is output from the wavelength selector 1A to the coupler 9A, the outputs of the coupler 9B and the wavelength selector module are selected by the wavelength selector 1A. Of the light, light other than the supervisory control light wavelength is output. When an RF signal having a frequency corresponding to the monitor control light wavelength is applied to the wavelength selection unit 1A, the monitor control light is input to the monitor 4A.

  The control section 3A receives the digital signal output from the monitor section 4A and outputs a control signal for defining the frequency, amplitude and phase generated from the RF signal generation sections 2A and 2B. The control unit 3A has a configuration shown in FIG. 16B as in the first embodiment.

(Description of Operation of Second Embodiment)
Next, the operation of the wavelength selection module according to the second embodiment of the present invention will be described.

  The wavelength selection module shown in FIG. 5 according to the second embodiment of the present invention uses a supervisory control light to correct the relationship between the frequency of the RF signal applied to the AOTF as the wavelength selection unit 1A and the AOTF selection wavelength. Wavelength selection module.

  In the second embodiment, of the split light of the coupler 9A, the light serving as the output light of the wavelength selection module is input to the filter 5C for blocking the supervisory control light and to the monitor 4A for monitoring the supervisory control light. The light is provided with a filter 5D that blocks WDM signal light and the like other than the supervisory control light.

  By providing the filters 5C and 5D, the operation of changing the RF signal applied to the wavelength selector 1A so as to select the supervisory control light can be performed without affecting the operation of selecting the WDM signal light. Therefore, the operation of correcting the relationship between the RF signal and the selected wavelength can be performed independently of the operation of selecting the WDM signal light.

  As a result, for example, the time allowed when selecting a new wavelength, such as a wavelength switch used for a burst switching method, is short, and the relationship between the RF signal frequency and the selected wavelength is selected before selecting a new wavelength. Even when the adjustment cannot be performed, the relationship between the RF signal frequency and the selected wavelength can always be adjusted, so that when selecting light of a new wavelength, the correct wavelength can be selected.

  In FIG. 5, the supervisory control light and the WDM signal light input to the wavelength selection module are input to the wavelength selection unit 1A. RF signals including a plurality of frequencies are input from the RF signal generators 2A and 2B to the RF signal input port of the wavelength selector 1A via the mixer 7A.

  As in the first embodiment, when the AOTF shown in FIG. 18 is used as the wavelength selector 1A, the input port of the wavelength selector 1A is an input (IN) port of the AOTF, and the output port of the wavelength selector 1A is Corresponds to AOTF branch (DROP) port. Of the WDM signal light input to the input (IN) port of the AOTF, the light of the wavelength corresponding to the frequency of the applied RF signal is output to the branch (DROP) port by mode conversion, and is output to the other wavelength. Light is output to the transmission (THRU) port. The RF signal output from the mixer 7A to the wavelength selector 1A is output from the RF signal generators 2A and 2B, and its frequency is determined by the controller 3A.

The frequencies of the RF signals output by the RF signal generators 2A and 2B are f ₁ and f ₂ , respectively, and the wavelength of the light to be mode-converted when the RF signals of the frequencies f ₁ and f ₂ are input to the wavelength selector 1A. Are λ ₁ and λ ₂ , respectively, light of wavelengths λ ₁ and λ ₂ is output from the branch (THRU) port of the AOTF that is the wavelength selection unit 1A.

  In the second embodiment, by utilizing the fact that the wavelength selector 1A can select a plurality of wavelengths, one or more wavelengths of light output as a selected wavelength module are selected as the selected wavelength, and the monitoring control light is selected. Wavelengths are selected.

  The supervisory control light is arranged at a wavelength apart from the wavelength of the WDM signal light so as not to affect the WDM signal light, and unlike the signal light, does not stop. Correction of the relationship between the RF signal frequency and the selected wavelength when the wavelength of the supervisory control light is shorter than the wavelength of the WDM signal light will be described below.

  As shown in the lower axis of the horizontal axis of FIG. 4, when AOTF is used as the wavelength selector 1A, the wavelength selected by the wavelength selector 1A decreases by increasing the RF frequency applied to the wavelength selector 1A.

  When the frequency of the RF signal output from the RF signal generation unit 2A is reduced in steps of 1 kHz from 180 MHz, the selected wavelength of the wavelength selection unit 1A increases due to the phenomenon of the frequency of the RF signal. It changes from the short wavelength side to the long wavelength side.

  Since the wavelength of the supervisory control light is longer than the shortest wavelength of the WDM signal light, the frequency of the RF signal is reduced, and the wavelength selected by the wavelength selector is changed to a longer wavelength. Since only the wavelength of the monitor control light is transmitted by the filter 5D, when the intensity of the monitor control light monitored by the monitor unit 4A becomes maximum, the frequency of the RF signal applied to the wavelength selection unit 1A is changed to It is recorded as an RF frequency f-OSC corresponding to the wavelength λ-OSC of the supervisory control light.

  As described in the first embodiment, if the rate of change of the optical wavelength with respect to the RF signal frequency is stored in advance, the RF signal frequency corresponding to a certain optical wavelength can be obtained to respond to light of an arbitrary wavelength. RF signal frequency can be obtained. In the second embodiment, since the frequency of each channel of the WDM signal light can be obtained from the monitor control signal or the like, the RF signal frequency f-OSC corresponding to the wavelength λ-OSC of the monitor control light is obtained. An RF signal frequency corresponding to the optical wavelength of each channel of the WDM signal light can be obtained.

  Therefore, even if the relationship between the RF signal frequency and the selected wavelength changes due to the temperature change of the wavelength selection unit, the change in the RF frequency and the selected wavelength relationship can be corrected by using the supervisory control light.

  As described above, in order to determine the frequency of the RF signal that gives the maximum value of the light intensity, the light intensity detection unit converts the optical signal of the predetermined wavelength while changing the frequency of the RF signal at the first frequency interval, for example, 1 KHz. The operation of detecting and determining the first maximum value at which the light intensity becomes maximum is called scanning.

  After detecting the RF signal frequency f-OSC corresponding to the supervisory control light by the above-described scanning, the tracking process described below is performed to respond to the characteristic change of the wavelength selector 1A and correct the change in the relationship between the RF frequency and the selected wavelength. It can be performed.

  Frequency tracking refers to periodically changing the frequency slightly before and after the RF frequency corresponding to the target light wavelength and searching for a frequency at which the monitored selected light intensity is maximized. The RF frequency corresponding to the target optical wavelength changes due to changes in the characteristics of the AOTF due to changes in the surrounding environment such as changes in temperature and aging, but following the change by selecting the target light by scanning and then performing frequency tracking Then, the RF frequency corresponding to the supervisory control light wavelength can be obtained.

  In the second embodiment, by providing the filter 5C, even if the supervisory control light is selected by the wavelength selection unit 1A, it is not output to the output (OUT) of the wavelength selection module. Even if scanning or tracking is performed to determine the frequency, the output (OUT) of the wavelength selection module is not affected, so the relationship between the supervisory control light wavelength and the RF signal frequency is updated at regular intervals by tracking. By updating the relationship between the RF signal frequency and the selected wavelength of the wavelength selector 1A, the relationship between the RF signal frequency and the selected wavelength can be constantly adjusted. You can make a selection.

  With this, when the wavelength selector selects WDM signal light, it is possible to continue to select the target signal light by tracking, and when selecting a WDM signal light of a new wavelength, monitoring and control are performed. A new target signal light can be selected based on the relationship between the RF signal frequency and the selected wavelength updated by the light tracking.

  When an RF signal is applied from the outside and wavelength selection is performed by AOTF, the selected wavelength changes according to the frequency of the RF signal, and the selected wavelength light intensity changes according to the intensity of the RF signal. FIG. 10 shows the relationship between the signal intensity of the RF signal and the intensity of the selected wavelength.

  As shown in FIG. 10, the intensity of the selected wavelength becomes maximum at a specific RF signal intensity. Power tracking refers to changing the RF signal intensity at the RF frequency corresponding to the target optical wavelength and searching for the RF signal intensity at which the monitored selected light intensity is maximized.

  When the WDM signal light is selected by the wavelength selection unit 1A, the frequency and power tracking are performed to control the frequency and intensity of the RF signal corresponding to the target optical wavelength and maximizing the optical output. You.

  In the second embodiment, by providing the filter 5C, even if the monitoring control light is selected by the wavelength selection unit 1A, it is not output to the output (OUT) of the wavelength selection module. Here, by using the relationship between the RF signal intensity and the output light intensity shown in FIG. 10, the filter characteristics of the filter 5C with respect to the monitor control light wavelength can be relaxed.

  That is, since the monitor unit 4A monitors the intensity of the supervisory control light and does not need to monitor the signal included in the supervisory control light, the intensity of the supervisory control light by the wavelength selector 1A selects the WDM signal light. It may not be as strong as it might be. As shown in FIG. 10, by reducing the intensity of the RF signal, the intensity of the light output from the wavelength selector 1A is reduced. The intensity of the RF signal corresponding to the monitor control light wavelength is reduced, and the output of the monitor control light by the wavelength selector 1A is suppressed to an intensity sufficient for the monitor unit 4A to monitor the monitor control light. Since the monitoring control light intensity decreases, the monitoring control light is not output to the output of the wavelength selection module, and the filter characteristic for the monitoring control light wavelength required for the filter 5C is loosened. Insertion loss can be suppressed.

  As described above, according to the second embodiment of the present invention, the supervisory control light and the light of the target wavelength are selected, the supervisory control light is continuously selected by scanning and tracking, and the temperature change of the wavelength selector is changed. The wavelength selection module is configured to correct the relationship between the RF signal frequency and the selected wavelength due to the above, and to arbitrarily switch the light of the target wavelength.

[C] Third Embodiment Next, FIG. 6 shows a wavelength selection module according to a third embodiment of the present invention. The wavelength selection module according to the third embodiment includes a wavelength selection unit 1A capable of selecting a plurality of wavelengths, a control unit (CTRL) 3A, RF signal generation units (RF OSC) 2A to 2B, a mixing unit (Mixer) 7A, and a monitor. This is a wavelength selection module including units (MON) 4A and 4B, a reference light generator (REF) 6A, an optical attenuator (ATT) 12A, couplers 9A and 9B, and a wavelength separation filter 8A. The configurations and operations of the wavelength selector 1A, the RF signal generators 2A to 2B, the mixer 7A, the coupler 9A, the monitor 4A, the wavelength separation filter 8, and the optical filters 5A to 5B are the same as those in the first embodiment.

  The reference light output from the reference light generator 6A is used to correct a phenomenon in which the wavelength selected by the wavelength selector 1A changes with temperature. Since the reference light generation unit has a mechanism that makes the wavelength of the output light constant inside, even if the temperature of the wavelength selection unit changes and the relationship between the RF signal frequency and the selection wavelength of the wavelength selection unit fluctuates, the RF The relationship between the RF signal frequency and the wavelength selected by the wavelength selection unit can be determined and corrected by changing the signal frequency and determining the frequency of the RF signal by which the wavelength selection unit selects the reference light wavelength. The output of the reference light generation unit 6A is adjusted in light intensity by the ATT 12A, multiplexed with the input light of the wavelength selection module by the coupler 9A, and input to the input port of the wavelength selection unit 1A.

  The monitor unit 4A inputs the light demultiplexed by the coupler 9A and outputs the intensity as a digital signal to the control unit 3A. The configuration of the monitor unit 4A is the same as that of the monitor unit in the first embodiment. A digital signal associated with the input light intensity obtained by the current-voltage conversion Log amplifier having a wide dynamic range is transmitted to the control unit 3A. Output.

  In the third embodiment, since the light obtained by multiplexing the input light of the wavelength selection module and the reference light is input to the input port of the wavelength selection unit 1A, the input light of the wavelength selection module is input to the monitor unit 4A. The light having a wavelength corresponding to the RF signal frequency applied to the wavelength selector 1A is input from the light obtained by multiplexing the reference light and the reference light.

  The control section 3A receives the digital signal output from the monitor section 4A and outputs a control signal for defining the frequency, amplitude and phase generated from the RF signal generation sections 2A and 2B. The control unit 3A has a configuration shown in FIG. 16B as in the first embodiment.

(Configuration of reference light generator)
As shown in FIG. 17, the reference light generating unit 6A includes an LD (Laser Diode) unit 42A having a wavelength fixing function and a control circuit therefor. Inside the LD unit 42A, a PD (Photo Diode) 36A that receives the output light of the LD 35A and a PD 36B that receives the light obtained by filtering the output light of the LD 35A by the filter 37A monitor the optical output of the LD 35A. The output currents of the PDs 36A and 36B are converted into voltages by PD monitor circuits (PD MON) 34A and 34B, respectively, converted into digital signals by AD converters (ADCs) 31B and 31C, and input to the control unit 3B. You.

  The temperature of the LD unit 42A is monitored by a temperature control unit (TEMP CTRL) 41A through a thermistor 38A, and the temperature control unit 41A is controlled by a temperature control circuit 39A (TEC) through a temperature control circuit driver (TEC DRV) 40A. And the temperature of the LD section 42A. The temperature information of the LD section 42A monitored by the temperature control section is converted into a digital signal by the AD converter 31A and input to the control section 3A.

  The control unit 3B controls the temperature control unit 41A through the DA converter 32A from the information on the output currents of the PDs 36A and 36B in the LD unit 42A obtained through the AD converters 31B and 31C, and changes the temperature of the LD unit 42A. Then, control is performed so that the wavelength of the output light from the LD 35A becomes constant. Further, the control unit 3B can control the LD driver (LD DRV) 33A through the DA converter 32B, thereby changing the current flowing to the LD 35A and changing the output light intensity of the LD unit 42A.

When the reference light generation unit shown in FIG. 17 is used in combination with an external device, for example, in FIG. 5, the control unit 3B in FIG. 17 may be different from the control unit 3A in FIG. The control unit 3A of FIG. 5 may double as the control unit 3B of FIG.
(Description of Operation of Third Embodiment)
Next, the operation of the wavelength selection module according to the third embodiment of the present invention will be described.

  The wavelength selection module according to the third embodiment of the present invention shown in FIG. 6 has a configuration in which reference light is multiplexed to the input of the wavelength selection unit of the wavelength selection module according to the first embodiment.

  As in the second embodiment, in the third embodiment, by providing the filters 5C and 5D, the operation of changing the RF signal applied to the wavelength selection unit 1A so as to select the reference light is performed by the WDM signal. Since the operation for selecting the light can be performed without affecting the operation for selecting the light, the operation for correcting the relationship between the RF signal and the selected wavelength can be performed independently of the operation for selecting the WDM signal light.

  In FIG. 6, the reference light output from the reference light generation unit 6A and the input light of the wavelength selection module are multiplexed by the coupler 9A and input to the input port of the wavelength selection unit 1A. The wavelength selector 1A selects, from the input light, light having a wavelength corresponding to the frequency of the RF signal applied from the mixer 7A, and outputs the selected light to the coupler 9A.

  In the third embodiment, when the temperature of the wavelength selector changes and the relationship between the RF signal frequency and the selected wavelength changes, the monitor unit 4A detects the reference light output from the reference light generator 6A. The relationship between the RF signal frequency and the selected wavelength can be corrected.

FIG. 4 shows the spectrum intensity input to the monitor unit 4A with respect to the wavelength. In a third embodiment, the wavelength of the output reference light of the reference light generating unit 6A and lambda _ref1, the wavelength lambda _ref1 of the reference light is set to be longer than the longest wavelength of the signal light. Further, the reference light generator 6A and the ATT 12A are set so that the reference light is observed by the monitor 4A at an intensity lower than the intensity of the signal light and higher than the side lobe intensity of the signal light.

  As shown in the lower axis of the horizontal axis of the graph of FIG. 4, the selected wavelength of the wavelength selector 1A is decreased by increasing the RF frequency applied to the wavelength selector 1A, so that the output of the RF signal generator 2A is changed. By observing the output of the monitor unit 4A, the spectrum shown in FIG. 4 can be obtained.

In FIG. 4, λ _{1 to} λ ₄ are signal lights selected by the wavelength selector 1A, λ _1SL is a short-wavelength side lobe of the signal light of wavelength λ ₁ , and λ _ref1 is a reference light detected by the monitor 4A. The peak position in each case is shown. The right vertical scale number indicates the intensity of light output to the wavelength selection module output (OUT), and the central scale number is branched by the coupler 9A or 9B, and the PD 55A of the monitor unit 4A or 4B (FIG. 16 (a)) shows the current value due to the light incident thereon, and the scale numbers on the left side show the output voltage of the current-voltage conversion Log amplifier 56A (FIG. 16 (a)). By using the log amplifier 56A, light in a wide intensity range from strong light to weak light can be converted into the input range of the AD converter 31A and transmitted to the control unit 3A.

  Hereinafter, a method for correcting the relationship between the RF signal frequency and the selected wavelength will be described with reference to FIGS.

  In the third embodiment, as in the first embodiment, the RF signal applied to the wavelength selector 1A has only one frequency. FIG. 3C shows the relationship between the WDM signal light and the selected wavelength when the wavelength selected by the wavelength selector 1A is reduced from the longer wavelength side to the shorter wavelength side. The horizontal axis represents the wavelength, and the vertical axis represents the light intensity. , And are represented schematically. When the frequency of the RF signal output from the RF signal generation unit 2A is increased in steps of 1 kHz from 170 MHz, the selected wavelength of the wavelength selection unit 1A decreases due to the increase in the frequency of the RF signal. As a result, the wavelength selected by the wavelength selector 1A changes from the long wavelength side to the short wavelength side.

As described above, the reference light is observed by the monitor unit 4A at an intensity smaller than the intensity of the signal light and higher than the side lobe intensity of the signal light, and has a spectrum indicated by λ _ref1 in FIG. The side lobe of the reference light is not discriminated from the signal light by 3A. Since the side lobe of the reference light is smaller than the intensity of the side lobe of the signal light, the reference light is not discriminated as the side lobe of the signal light.

Since the wavelength λ _{ref1 of the} reference light is longer than the longest wavelength of the WDM signal light, by increasing the frequency of the RF signal and changing the wavelength selected by the wavelength selector to the shorter wavelength side, the wavelength selector reference light is Is monitored. When the intensity of the reference light monitored by the monitor unit 4A becomes maximum, the frequency of the RF signal applied to the wavelength selection unit 1A is recorded as an RF frequency f _ref1 corresponding to the wavelength λ _{ref1 of the} reference light.

  As described in the first embodiment, if the rate of change of the optical wavelength with respect to the RF signal frequency is stored in advance, the RF signal frequency corresponding to a certain optical wavelength can be obtained to respond to light of an arbitrary wavelength. RF signal frequency can be obtained. In the third embodiment, since the frequency of each channel of the WDM signal light can be obtained from the monitoring control signal or the like, by detecting the RF signal frequency when the reference light is selected, each channel of the WDM signal light can be detected. The RF signal frequency corresponding to the light wavelength can be obtained.

  Therefore, even if the relationship between the RF signal frequency and the selected wavelength changes due to the temperature change of the wavelength selector, the change in the RF frequency and the selected wavelength relationship can be corrected by using the reference light.

In the above description, it is assumed that the wavelength λ _{ref1 of the} reference light is longer than the longest wavelength of the signal light, and the wavelength selected by the wavelength selector 1A is changed from the long wavelength side to the short wavelength side, whereby the monitor unit 4A Conversely, the reference light was detected. On the contrary, the wavelength λ _{ref1 of the} reference light was set to be shorter than the shortest wavelength of the signal light, and the wavelength selected by the wavelength selector 1A was changed from the short wavelength side to the long wavelength side to monitor. Even if the unit 4A detects the reference light, it is possible to correct the change in the relationship between the RF frequency and the selected wavelength by the same method.

  As described above, according to the third embodiment of the present invention, by combining the reference light with the input light, one wavelength selector is used to select light of two wavelengths that are not wavelength-multiplexed, At the same time as outputting, a wavelength selection module that corrects the relationship between the RF signal frequency and the selected wavelength due to the temperature change of the wavelength selection unit can be simply configured.

[D] Fourth Embodiment FIG. 7 shows a wavelength selection module according to a fourth embodiment of the present invention. The wavelength selection module according to the fourth embodiment includes a wavelength selection unit 1A capable of selecting a plurality of wavelengths, a reference light generation unit (REF) 6A, an optical attenuator (ATT) 12A, a control unit (CTRL) 3A, and an RF signal generation unit. (RF OSC) 2A to 2B, a mixing unit (Mixer) 7A, monitor units (MON) 4A to 4B, optical filters 5C to 5D, and a wavelength selection module including couplers 9A to 9C. The operations of the wavelength selector 1A, the RF signal generators 2A to 2B, the mixer 7A, and the couplers 9A to 9B are the same as in the second embodiment. The configurations and operations of the reference light generator 6A and the optical attenuator 12A are the same as in the third embodiment.

  The wavelength selection module according to the second embodiment of the present invention shown in FIG. 7 performs correction of the relationship between the frequency of the RF signal applied to the AOTF, which is the wavelength selection unit 1A, and the AOTF selection wavelength by the reference light generation unit 6A. This is a wavelength selection module that uses the output reference light.

  The optical filter 5C is a filter that attenuates the wavelength of the reference light, and sets the wavelength of the reference light so that the output of the wavelength selection module output through the coupler 9B does not include the reference light among the lights branched by the coupler 9A. Blocks and transmits other wavelengths of light.

  On the other hand, the optical filter 5D is a filter that selectively transmits light having the reference light wavelength from the light branched from the coupler 9A, and the light after the filter is input to the monitor 4A. Selectively transmitting the wavelength of the reference light means that only the wavelength of the reference light is transmitted out of the light output from the wavelength selection unit 1A, and for example, is higher than the wavelength of the wavelength-multiplexed signal light. When the wavelength of the reference light is short, a low-pass filter can be used. When there is reference light between the wavelengths of the wavelength-multiplexed signal light, a band-pass filter can be used.

  In the fourth embodiment, since the light having the wavelength corresponding to the applied RF signal frequency is output from the wavelength selector 1A to the coupler 9A, the output of the coupler 9B and the wavelength selector module is selected by the wavelength selector 1A. Of the light, light other than the reference light wavelength is output. When an RF signal having a frequency corresponding to the wavelength of the reference light is applied to the wavelength selector 1A, the monitor 4A receives the reference light.

  As in the second embodiment, by providing the filters 5C and 5D, the operation of changing the RF signal applied to the wavelength selector 1A so as to select the reference light affects the operation of selecting the WDM signal light. Therefore, the operation of correcting the relationship between the RF signal and the selected wavelength can be performed independently of the operation of selecting the WDM signal light.

[E] Fifth Embodiment Next, FIG. 8 shows a wavelength selection module according to a fifth embodiment of the present invention. The wavelength selection module according to the fifth embodiment includes a wavelength selection unit 1A, a control unit (CTRL) 3A, RF signal generation units (RF OSC) 2A to 2B, a mixing unit (Mixer) 7A, and a monitoring unit (MON) 4A to 4B, a wavelength selection module composed of a wavelength separation filter 8A as a demultiplexing unit, couplers 9C to 9E, optical filters 5A to 5B, reference light generation units (REF) 6A to 6B, and optical attenuators (ATT) 12A to 12B. . The configurations and operations of the wavelength selector 1A, the RF signal generators 2A to 2B, the mixer 7A, the wavelength separation filter 8A, and the optical filters 5A to 5B are the same as those in the first embodiment.

  The first and second reference lights output from the reference light generators 6A and 6B are used to correct a phenomenon in which the wavelength selected by the wavelength selector 1A changes with temperature. Since the reference light generation unit has a mechanism that makes the wavelength of the output light constant inside, even if the temperature of the wavelength selection unit changes and the relationship between the RF signal frequency and the selection wavelength of the wavelength selection unit fluctuates, the RF The relationship between the RF signal frequency and the wavelength selected by the wavelength selection unit can be determined and corrected by changing the signal frequency and determining the frequency of the RF signal by which the wavelength selection unit selects the reference light wavelength.

  In the fifth embodiment, the first and second reference lights output by the reference light generation units 6A and 6B are combined with the input light of the wavelength selection module, input to the wavelength selection unit 1A, and monitored. Since the relationship between the reference light and the RF signal frequency is independently corrected in each of 4A and 4B, the relationship between the RF signal frequency and the selected wavelength can be accurately determined, and the phenomenon that the selected wavelength of the wavelength selector 1A changes with temperature. Can be corrected more accurately.

  The first and second reference lights output from the reference light generators 6A and 6B are adjusted in light intensity by the ATTs 12A and 12B, respectively, multiplexed with the input light of the wavelength selection module by the coupler 9C, and Enter 1A.

  As in the first embodiment, the wavelength separation filter 8A is a filter that separates the output from the coupler 9A into the optical filters 5A and 5B. The wavelength separation filter 8A according to the fifth embodiment separates the light in the C band wavelength region into the optical filter 5A and the light in the L band wavelength region into the optical filter 5B of the light output from the coupler 9A. And output.

  The optical filter 5A is an optical filter that transmits only the light in the C band region and attenuates the light other than the C band region of the light split by the wavelength separation filter 8A, so that the C band selected by the wavelength selector 1A is used. Is output to the output (OUT) port 1 of the optical filter.

  Similarly, the optical filter 5B is an optical filter that transmits only light in the L-band region, and attenuates light other than the L-band region of the light split by the wavelength separation filter 8A. Only the L band light is output to the output (OUT) port 2 of the optical filter.

  The monitoring units 4A and 4B receive the output lights of the optical filters 5A and 5B, which are branched by the couplers 9D and 9E, respectively, and output the intensity as a digital signal to the control unit 3A. The configuration of the monitoring units 4A and 4B is the same as that of the monitoring unit in the first embodiment, and converts the digital signal associated with the input light intensity obtained by the current-voltage conversion Log amplifier having a wide dynamic range into the control unit. Output to 3A.

  The control unit 3A receives the digital signals output from the monitor units 4A and 4B, and outputs a control signal that defines the frequency, amplitude, and phase generated from the RF signal generation units 2A and 2B. The control unit 3A has a configuration shown in FIG. 16B as in the first embodiment.

(Description of Operation of Fifth Embodiment)
Next, the operation of the wavelength selection module according to the fifth embodiment of the present invention will be described.

  In the wavelength selection module according to the fifth embodiment of the present invention shown in FIG. 8, the input WDM signal light is multiplexed with the first and second reference lights output by the reference light generators 6A and 6B, It is input to the wavelength selector 1A.

Respectively f ₁ and f ₂ the frequency of the RF signal output by the RF signal generator 2A and 2B, is mode conversion when the RF signal of frequency f ₁ and f ₂ is input to the wavelength selection portion 1A, the branch (DROP ) Let the wavelengths of the light output from the ports be λ ₁ and λ ₂ respectively.

Similarly to the first embodiment, if f ₁ and f ₂ are determined so that λ ₁ is in the wavelength band of the C band and λ ₂ is in the wavelength band of the L band, the wavelength separation filter 8A becomes Since the coupler outputs the light in the wavelength region to the optical filter 5A and the light in the L band wavelength region to the optical filter 5B, the light of wavelength λ ₁ is output to the optical filter 5A, and the light of wavelength λ ₂ is Output to the optical filter 5B.

Since the optical filter 5A is an optical filter that transmits only the light in the C band region and the optical filter 5B is an optical filter that transmits only the light in the L band region, the light of the wavelength λ ₁ passes through the output (OUT) port 1 and the monitor unit through the optical filter 5A. The light having the wavelength λ ₂ is output to the output (OUT) port 2 and the monitor unit 4B through the optical filter 5B.

Therefore, the monitor unit 4A indicates the intensity of the light of the wavelength λ _{1 in} the C band wavelength band of the light selected by the wavelength selection unit 1A, and the monitor unit 4A indicates the L band of the light selected by the wavelength selection unit 1A. and it outputs the intensity of the light having the wavelength lambda ₂ in the wavelength band of the each control unit 3A as a digital signal.

Thereby, in the fifth embodiment, the control unit 3A independently and simultaneously obtains the light intensity information of the wavelength λ _{1 and} the light intensity of the wavelength λ ₂ from the information of the monitor units 4A and 4B.

  Hereinafter, a method of correcting the relationship between the RF signal frequency and the selected wavelength will be described with reference to FIG.

In the fifth embodiment, the reference lights output from the reference light generating units 6A and 6B are referred to as reference lights 1 and 2, respectively, and the wavelengths of the reference lights 1 and 2 are referred to as λ _ref1 and λ _ref2 , respectively. . Further, the wavelength λ _ref1 of the reference light 1 is shorter than the shortest wavelength of the signal light and the wavelength that transmits the optical filter 5A, the wavelength λ _ref2 of the reference light 2 is longer than the longest wavelength of the signal light, and , The wavelength that transmits the optical filter 5B.

  Similarly to the third embodiment, the reference light 1 and the reference light 2 are observed by the monitor unit 4A and the monitor unit 4B at an intensity lower than the intensity of the signal light and higher than the side lobe intensity of the signal light, respectively. The reference light generators 6A and ATT12A and the reference light generators 6B and ATT12B are set so as to perform the above operations.

FIG. 3D shows the WDM signal light when the selected wavelength of the wavelength selection unit 1A is reduced from one longer wavelength to the shorter wavelength and one wave is increased from the shorter wavelength to the longer wavelength. The relationship with the selected wavelength is schematically shown with the horizontal axis representing wavelength and the vertical axis representing light intensity. The output signal frequency f ₁ of the RF signal generator 2A is changed from the high frequency side to the low frequency side, by changing the selected wavelength lambda ₁ of the wavelength selection portion 1A from the short wavelength side to the long wavelength side, the monitor unit 4A detects the reference light 1. Similarly, the output signal frequency f ₂ of the RF signal generator 2B is changed from the low frequency side to the high frequency side, by changing the selected wavelength lambda ₂ of the wavelength selection portion 1A from the long-wavelength side to the shorter wavelength side , The monitor unit 4B detects the reference light 2.

In the fifth embodiment, of the output of the wavelength selector 1A, the light in the C band wavelength region and the light in the L band wavelength region are independently and simultaneously transmitted by the monitor units 4A and 4B, respectively. Since the frequency of the RF signal output from the RF signal generators 2A and 2B can be changed and output independently of each other, the RF signal frequency f _{ref1 satisfying} λ _ref1 = λ ₁ can be monitored by the monitor units 4A and 4B. And the RF signal frequency f _{ref2 satisfying} λ _ref2 = λ ₂ can be searched independently and simultaneously.

Thus, RF signal of frequency f _ref1, the frequency f _ref2 obtain the RF signal when selecting the lambda _ref2, the rate of change of the light wavelength for RF signal frequency when the wavelength selecting unit 1A selects the lambda _ref1 Can be obtained, and the RF signal frequency corresponding to the target light wavelength can be obtained without storing the change rate in advance.

  As in the third embodiment, the frequency of each channel of the WDM signal light can be obtained from a monitoring control signal or the like. Therefore, the fifth embodiment also corresponds to the optical wavelength of each channel of the WDM signal light. The RF signal frequency can be determined.

  In the fifth embodiment, since the change rate of the light wavelength with respect to the RF signal frequency can be directly obtained, it is not necessary to use the change rate of the light wavelength with respect to the RF signal frequency. Thereby, it is not necessary to correct the deviation of the calculated RF signal frequency and the deviation of the selected wavelength due to the deviation of the previously stored change rate from the actual change rate by another means such as tracking. It has the advantage that.

  Further, since the wavelength searches for the reference light 1 and the reference light 2 are independently and simultaneously performed by the monitor units 4A and 4B, the search time is one wave, although the wavelength search for the reference light is performed for two waves. It can fit as much as the case.

  As described above, according to the fifth embodiment of the present invention, two wavelengths of the reference light are multiplexed with the input light, and the output that is demultiplexed for each wavelength band is monitored, so that one wavelength selector can be used. Can be used to select and output two wavelengths of light that are not wavelength multiplexed, and at the same time, the relationship between the RF signal frequency and the selected wavelength due to the temperature change of the wavelength selector can be determined using two reference light waves. A wavelength selection module that can be accurately corrected can be simply configured.

[F] Sixth Embodiment Next, FIG. 9 shows a wavelength selection module according to a sixth embodiment of the present invention. The wavelength selection module according to the sixth embodiment includes a wavelength selection unit 1A to 1D, a control unit (CTRL) 3A, an RF signal generation unit (RF OSC) 2A to 2F, a mixing unit (Mixer) 7A, and a monitor unit (MON). 4A to 4F, couplers 9A to 9G, optical filters 5A to 5B, reference light generators (REF) 6A to 6B, and optical attenuators (ATT) 12A to 12B.

  The wavelength selectors 1A to 1D in FIG. 9 are wavelength selectors under the same environment, and for example, an integrated AOTF array can be used.

  As in the fifth embodiment, the first and second reference lights output from the reference light generators 6A and 6B are used to correct a phenomenon in which the wavelength selected by the wavelength selector 1D changes with temperature. . Since the reference light generation unit has a mechanism that makes the wavelength of the output light constant inside, even if the temperature of the wavelength selection unit changes and the relationship between the RF signal frequency and the selection wavelength of the wavelength selection unit fluctuates, the RF The relationship between the RF signal frequency and the wavelength selected by the wavelength selection unit can be determined and corrected by changing the signal frequency and determining the frequency of the RF signal by which the wavelength selection unit selects the reference light wavelength.

  In the sixth embodiment, the first and second reference lights output by the reference light generators 6A and 6B are multiplexed with the input light of the wavelength selection module by the coupler 9G and then split by the coupler 9A. , Is input to the wavelength selector 1D, and the monitors 4A and 4B independently correct the relationship between the reference light and the RF signal frequency, so that the relationship between the RF signal frequency and the selected wavelength can be accurately obtained, and the wavelength selector The correction of the phenomenon in which the selected wavelength of 1A changes with temperature can be made more accurate.

  The first and second reference lights output from the reference light generators 6A and 6B are adjusted in light intensity by the ATTs 12A and 12B, respectively, multiplexed with the input light of the wavelength selection module by the coupler 9G, and multiplexed by the coupler 9A. The signals are demultiplexed and input to the wavelength selectors 1A to 1D.

  The wavelength selectors 1A to 1C select light having a wavelength corresponding to the RF signal frequency output from the RF signal generators (RF OSC) 2D to 2F, respectively, and output them as outputs (OUT1 to OUT3) of the wavelength selection module. I do. Outputs of the wavelength selectors 1A to 1C are branched by couplers 9B to 9D, respectively, and monitored by monitor units (MON) 4A to 4C.

  On the other hand, by applying the RF signal through the mixing unit 7A so that the wavelength selection unit 1D selects the signal light of the target wavelength and the first and second reference lights, the RF signal is applied in the same manner as in the fourth embodiment. The relationship between the frequency and the wavelength selected by the wavelength selector can be determined and corrected.

  The optical filter 5E is a filter for attenuating the wavelengths of the first and second reference lights. Of the light branched by the coupler 9F, the first and second lights are output to the output (OUT4) of the wavelength selection module output through the coupler 9E. The first and second reference light wavelengths are blocked and light of other wavelengths is transmitted so that the second reference light is not included.

  On the other hand, the optical filters 5G and 5H are filters that selectively transmit light of the first and second reference light wavelengths, respectively, from the light branched by the coupler 9F, and the light after the filtering is applied to the monitor unit 4B and the monitor unit 4B, respectively. 4A.

  Thereby, when the RF signal is applied through the mixing unit 7A so that the wavelength selection unit 1D selects the signal light of the target wavelength and the first and second reference lights, of the output light branched by the coupler 9F, The signal light of the target wavelength is output to OUT4, and the first and second reference lights are output to monitor units 4B and 4A, respectively.

  In the sixth embodiment, as in the second and fourth embodiments, the wavelength selecting unit 1D and the control unit 3A continuously select the first and second reference lights by scanning and tracking, and select the wavelengths. While correcting the relationship between the RF signal frequency and the selected wavelength due to the temperature change of the selector 1D, it is possible to arbitrarily switch the light of the target wavelength.

  The wavelength selectors 1A to 1D are under the same environment, and it can be considered that there is almost no difference in the relationship between the RF signal frequency and the selected wavelength due to the temperature change of the wavelength selector. By correcting the relationship between the signal frequency and the selected wavelength, the relationship between the RF signal frequency of the wavelength selectors 1A to 1D and the selected wavelength is corrected.

  Thus, by performing control for correcting the relationship between the RF signal frequency and the selected wavelength on one wavelength selector, correction can be performed on a plurality of wavelength selectors, thereby reducing costs. Can be.

[G] Seventh Embodiment Next, FIG. 11 shows an OADM device according to a seventh embodiment of the present invention. The OADM device according to the seventh embodiment includes optical couplers 9A to 9D, optical amplifiers 11A to 11I, wavelength selection modules 10A to 10D, transponder units 15A to 15B, optical attenuators (ATTs) 12A to 12H, and a BRF (band stop optical filter). Band Rejection Filter) 16A to 16B. Further, the transponder unit 15A includes optical receivers 13A to 13D and optical transmitters 14A to 14D, and the transponder unit 15B includes optical receivers 13E to 13H and optical transmitters 14E to 14H.

  Each of the wavelength selection modules 10A to 10D is a wavelength selection module according to the present invention using a wavelength selection unit, and selects and outputs one light in each of the C-band and L-band wavelength bands.

  The BRFs 16A and 16B use the rejection function of the wavelength selection unit. Among the light input from the insertion (ADD) port, the light corresponding to the frequency of the applied RF signal is transmitted to the transmission (THRU) port. Output. Further, of the light input from the input (IN) port, the light corresponding to the frequency of the applied RF signal is output to the branch (DROP) port and not output to the transmission (THRU) port.

In the OADM apparatus shown in FIG. 11, light of wavelengths λ _C1 , λ _C2 , λ _C3 , λ _C4 in the wavelength band of _C band and wavelength λ _{L1 in} the wavelength band of L band are inputted from the input WDM signal light. , Λ _L2 , λ _L3 , and λ _L4 are branched into single-wavelength light and output, and the inserted light is _divided into wavelengths λ _C5 , λ _C6 , λ _C7 , λ _C8 , and λ _L5. , Λ _L6 , λ _L7 , and λ _L8 will be described as being inserted into the WDM signal light, multiplexed and output.

  The WDM signal light input to the input port of the OADM device is split by the coupler 9A and input to the input (IN) port of the BRF 16A and the optical amplifier 11A. The light amplified by the optical amplifier 11A is split by the coupler 9B and input to the optical devices 10A to 10D.

The optical devices 10A to 10D are optical devices according to the present invention, and the optical device 10A outputs light of wavelengths λ _C1 and λ _L1 to the branch optical ports of the OADM device, and similarly, the optical devices 10B to 10D Light of wavelengths λ _{C2 to} λ _C4 and λ _{L2 to} λ _L4 are output to the branch optical ports of the OADM device. Therefore, the eight optical devices λ _C1 to λ _C4 and λ _L1 to λ _L4 can be selected and output by the four optical devices 10A to 10D.

On the other hand, the light input to the insertion optical port 1 of the OADM device changes the wavelength of the signal light by the transponder unit 15A and outputs it as light of wavelengths λ _{C5 to} λ _C8 . The outputted lights of wavelengths λ _{C5 to} λ _C8 are amplified by the optical amplifiers 11B to 11E, adjusted in light intensity by ATTs 12A to 12D, multiplexed by the coupler 9C, and connected to the insertion (ADD) port of the BRF 16A. input.

Similarly, the light input to the insertion optical port 2 of the OADM device changes the wavelength of the signal light by the transponder unit 15B, and outputs it as light of wavelengths λ _{L5 to} λ _L8 . The outputted lights of wavelengths λ _{L5 to} λ _L8 are amplified by the optical amplifiers 11F to 11I, adjusted in light intensity by ATTs 12E to 12H, multiplexed by the coupler 9D, and connected to the insertion (ADD) port of the BRF 16B. input.

The WDM signal light demultiplexed by the coupler 9A is input to the input (IN) port of the BRF 16A, and light having wavelengths λ _{C5 to} λ _C8 is input to the insertion (ADD) port of the BRF 16A from the coupler 9C. In order to output the light input to the insertion (ADD) port to the transmission (THRU) port, an RF signal having a frequency corresponding to the wavelengths λ _{C5 to} λ _C8 is applied to the BRF 16A. ) Of the WDM signal light input to the port, the light of wavelengths λ _{C5 to} λ _C8 is output to the drop (DROP) port, so the light excluding wavelengths λ _{C5 to} λ _C8 is output to the transmission (THRU) port. Is done.

Similarly, the WDM signal light output from the transmission (THRU) port of the BRF 16B is input to the input (IN) port of the BRF 16B, and the wavelengths λ _{L5 to} λ _L8 from the coupler 9D are input to the insertion (ADD) port of the BRF 16B. Light is input. To output the light input to the insertion (ADD) port to the transmission (THRU) port, an RF signal having a frequency corresponding to the wavelengths λ _{L5 to} λ _L8 is applied to the BRF 16B. ) Of the WDM signal light input to the port, the light of wavelengths λ _{L5 to} λ _L8 is output to the drop (DROP) port, so the light excluding wavelengths λ _{L5 to} λ _L8 is output to the transmission (THRU) port. And output to the output port of the OADM device.

  FIG. 12 is a modification of the embodiment of FIG. In the OADM device shown in FIG. 12, the components denoted by the same reference numerals as those in FIG. 11 are the same members, and thus the description thereof will be omitted.

  The output light from the reference light generator 6A is input to the optical attenuator 12C so as to be adjusted to an arbitrary optical power. The light adjusted to a predetermined optical power by the optical attenuator 12C is input to the optical coupler 9E. In the optical coupler 9E, the WDM signal light separated by the optical coupler 9A and the light of the optical attenuator 12C are multiplexed and output. The output of the optical coupler 9E is input to the optical amplifier 11A and is amplified to a predetermined optical power. The output of the optical amplifier 11A is input to the optical coupler 9B. The optical coupler 9B separates the input amplified WDM signal light and the light from the reference light generating unit into a plurality of lights, and inputs the lights to the optical devices 10A to 10D.

  With this configuration, it is not necessary to provide the reference light source in each of the optical devices 10A to 10D, and the configuration can be simplified.

  In this drawing, the number of the reference light generator is one, but a plurality of reference lights may be used as shown in FIG. At this time, if a plurality of reference light generation units are used, a plurality of reference lights can be used.

  As described above, according to the seventh embodiment of the present invention, a variable wavelength selection module using one wavelength selection unit, which can select and output light of two wavelengths that are not wavelength-multiplexed, is used in the OADM device. By using the OADM device, it is possible to configure an OADM device capable of increasing the number of wavelengths to be dropped / inserted while suppressing the number of wavelength selection units to be used.

  In the first, third, and fifth embodiments, one light in the C-band wavelength band and one light in the L-band wavelength band are selected by one wavelength selection unit, and each wavelength is selected by a coupler. However, if the wavelength selected by the wavelength selector is in another wavelength band, the wavelength can be demultiplexed by the coupler, so that the number of waves that can be selected and output is not limited to two.

  For example, if the RF signal outputs from the three RF signal generators are mixed, C-band, L-band, and S-band light are selected by the wavelength selector and demultiplexed for each wavelength by the coupler, the first to fifth wavelengths are obtained. With the same configuration as the embodiment, it is possible to select and output light of three wavelengths that are not wavelength-multiplexed.

If the wavelength selection module capable of selecting and outputting these three wavelengths of light is used in the seventh embodiment and the configuration, it is used for an OADM device for dropping / inserting C-band, L-band, and S-band light. The number of wavelength selectors can be reduced.

(H) Supplementary notes The present application includes the inventions described in the following supplementary notes.

(Appendix 1)
A wavelength selecting unit that inputs light in which a plurality of different wavelengths of light are multiplexed, selects and outputs light of a plurality of wavelengths according to a control signal given from the outside,
A wavelength selection module including a demultiplexing unit that demultiplexes output light of the wavelength selection unit for each wavelength and outputs the demultiplexed light.

(Appendix 2)
The wavelength selection module according to claim 1, wherein
A wavelength selection module comprising means for inputting the output light of the demultiplexer and attenuating and outputting light of an unnecessary wavelength.

(Appendix 3)
A wavelength selector for selecting and outputting a plurality of wavelengths from an input light by an external control signal,
An optical filter including a demultiplexing unit that demultiplexes the output light of the wavelength selection unit into light of a plurality of wavelengths,
A reference light source that generates reference light for the filter;
A wavelength selection module including a multiplexing unit that multiplexes input light and the reference light and inputs the multiplexed light to the wavelength selection unit.

(Appendix 4)
The wavelength selection module according to claim 3, wherein
The demultiplexing means has a monitor output;
A control signal for controlling the wavelength selector when the light of the wavelength of the reference light source is output to the monitor output and a control signal for controlling the wavelength selector based on the wavelength of the reference light source are controlled. A wavelength selection module, characterized in that:

(Appendix 5)
The wavelength selection module according to claim 3, wherein
The reference light source generates light of a plurality of wavelengths,
The plurality of wavelengths separated by the demultiplexing unit are respectively monitored and output,
A control signal for controlling the wavelength selector when the light of the wavelength of the reference light source is output to the monitor output and a control signal for controlling the wavelength selector based on the wavelength of the reference light source are controlled. A wavelength selection module, characterized in that:

(Appendix 6)
A wavelength selection unit that receives a plurality of different wavelengths of light, selects and outputs a plurality of wavelengths of light according to a control signal given from the outside,
Branching means for branching the output of the wavelength selector into first and second lights;
A first filter that inputs the second light and selectively transmits light of a specific wavelength;
A control unit that adjusts a relationship between the control signal given to the wavelength selection unit and the selected wavelength based on the control signal, an output of the first filter, and a transmission wavelength of the filter. Wavelength selection module.

(Appendix 7)
A reference light source having a constant output wavelength,
Multiplexing means for multiplexing input light including a plurality of different wavelengths of light and output light of the reference light source,
A wavelength selection unit that inputs the output light of the multiplexing unit, selects and outputs light of a plurality of wavelengths according to a control signal given from the outside,
Branching means for branching the output of the wavelength selector into first and second lights;
A first filter that inputs the second light and selectively transmits light having an output light wavelength of the reference light source;
A control unit that adjusts a relationship between the control signal given to the wavelength selection unit and the selected wavelength based on the control signal, the output of the first filter, and the wavelength of the reference light source. Wavelength selection module.

(Appendix 8)
First and second reference light sources having a constant output wavelength;
Multiplexing means for multiplexing input light including light of a plurality of different wavelengths and output light of the first and second reference light sources;
A wavelength selection unit that inputs the output light of the multiplexing unit, selects and outputs light of a plurality of wavelengths according to a control signal given from the outside,
Branching means for branching the output of the wavelength selector into first to third light;
A first filter for inputting the second light and selectively transmitting light having an output light wavelength of the first reference light source;
A second filter that receives the third light and selectively transmits light having an output light wavelength of the second reference light source;
The control signal, the output of the first filter, and the wavelength of the first reference light source; and the control signal, the output of the second filter, and the relationship between the wavelength of the second reference light source, the wavelength A wavelength selection module comprising: a control unit that adjusts a relationship between a control signal supplied to the selection unit and a selected wavelength.

(Appendix 9)
9. The wavelength selection module according to claim 6, wherein the control unit controls the control signal so that the light selectively transmitted by the first or second filter is continuously selected by the wavelength selection unit. A wavelength selection module characterized by controlling the wavelength.

(Appendix 10)
The wavelength selection module according to any one of Supplementary Notes 6 to 8, wherein the control unit suppresses an output of the control signal corresponding to light selectively transmitted by the first or second filter, so that the control unit outputs the control signal. A wavelength selection module for suppressing output of a wavelength of light selectively transmitted by a first or a second filter to the first light.

(Appendix 11)
The wavelength selection module according to Supplementary Notes 6 to 8, wherein:
The wavelength selection module according to claim 1, further comprising a third filter that receives the first light and attenuates a wavelength of the light selectively transmitted by the first or second filter.

FIG. 2 shows a wavelength selection module according to the present invention. FIG. 4 is a diagram showing light intensity in each part of the wavelength selection module according to the present invention. The figure which shows the relationship between the selection wavelength and input light of the wavelength selection part used for the wavelength selection module by this invention. Diagram showing spectra of reference light and signal light FIG. 2 shows a wavelength selection module according to the present invention. FIG. 2 shows a wavelength selection module according to the present invention. FIG. 2 shows a wavelength selection module according to the present invention. FIG. 2 shows a wavelength selection module according to the present invention. FIG. 2 shows a wavelength selection module according to the present invention. Diagram showing the relationship between RF signal intensity applied to AOTF and output light intensity FIG. 1 is a diagram showing an optical add / drop multiplexer according to the present invention. FIG. 1 is a diagram showing an optical add / drop multiplexer according to the present invention. Diagram showing the configuration of the RF signal generator Diagram showing DDS configuration Diagram showing DDS configuration The figure which shows the structure of a monitor part and a control part. Diagram showing the configuration of the reference light generator Diagram showing the configuration of an acousto-optic tunable filter (AOTF) Diagram showing an optical add / drop multiplexer according to a conventional technique Diagram showing optical burst switch method

Explanation of reference numerals

1A Wavelength selector 2A-2B High frequency signal generator (RF OSC)
3A-3B control unit (CTRL)
4A-4B Monitor part (MON)
5A-5F Optical filters 6A-6B Reference light generator (REF)
7A Mixing section
8A Wavelength separation filters 9A to 9G Couplers 10A to 10D Wavelength selection modules 11A to 11C according to the present invention Optical amplifiers, optical amplifiers 12A to 12C Optical attenuators (ATT), optical attenuators 13A to 13B Optical receivers 14A to 14B Optical transmitters 15A-15B Transponders 16A-16B BRF (Band Rejection Filter)
20A to 20D Wavelength selector 21A using AOTF according to the prior art IDT (comb-shaped electrode)
22A SAW waveguides 23A-23B PBS (Polarizing beam splitter)
24A to 24F Optical waveguide 25A Absorber 26A Substrate 27A MPU unit 28A ROM unit 29A RAM unit 30A EEPROM unit 31A to 31C AD converter (ADC)
32A to 32C DA converter (DAC)
33A LD drive unit 34A PD monitor unit 35A Laser diode (LD)
36A-36B Photodiode (PD)
37A Filter 38A Thermistor 39A Temperature control circuit (TEC)
40A Temperature control circuit driver (TEC DRV)
41A Temperature control unit (TEMP CTRL)
42A LD section 51A-51B having wavelength fixing function DDS (Direct Digital Synthesizer)
52A-52D High-frequency band pass filter (BPF)
53A-53D High Frequency Amplifier (RF AMP)
54A Multiplier 55A Photodiode (PD)
56A Log amplifier for current-voltage conversion 57A Non-inverting amplifier 58A Low-pass filter for high frequency (LPF)
61A Phase calculators 62A-62B Amplitude converters 63A-63B DA converter (DAC)
64A to 64B Register 65A Reference clock multiplier 66A Digital multiplier 70 Optical burst switching network 71 Access network 73 Edge node 74 Relay node 80A to 80B Control packets 81A to 81B Burst data

Claims (8)

A wavelength selecting unit that inputs light in which a plurality of different wavelengths of light are multiplexed, selects and outputs light of a plurality of wavelengths according to a control signal given from the outside,
A wavelength selection module including a demultiplexing unit that demultiplexes output light of the wavelength selection unit for each wavelength and outputs the demultiplexed light.
The wavelength selection module according to claim 1, wherein
A wavelength selection module, comprising: means for inputting the output light of the demultiplexing means and attenuating and outputting light of an unnecessary wavelength.
A wavelength selection unit that receives a plurality of different wavelengths of light, selects and outputs a plurality of wavelengths of light according to a control signal given from the outside,
Branching means for branching the output of the wavelength selector into first and second lights;
A first filter that inputs the second light and selectively transmits light of a specific wavelength;
A control unit that adjusts a relationship between the control signal given to the wavelength selection unit and the selected wavelength based on the control signal, an output of the first filter, and a transmission wavelength of the filter. Wavelength selection module.
A reference light source having a constant output wavelength,
Multiplexing means for multiplexing input light including a plurality of different wavelengths of light and output light of the reference light source,
A wavelength selection unit that inputs the output light of the multiplexing unit, selects and outputs light of a plurality of wavelengths according to a control signal given from the outside,
Branching means for branching the output of the wavelength selector into first and second lights;
A first filter that inputs the second light and selectively transmits light having an output light wavelength of the reference light source;
A control unit that adjusts a relationship between the control signal given to the wavelength selection unit and the selected wavelength based on the control signal, the output of the first filter, and the wavelength of the reference light source. Wavelength selection module.
First and second reference light sources having a constant output wavelength;
Multiplexing means for multiplexing input light including light of a plurality of different wavelengths and output light of the first and second reference light sources;
A wavelength selection unit that inputs the output light of the multiplexing unit, selects and outputs light of a plurality of wavelengths according to a control signal given from the outside,
Branching means for branching the output of the wavelength selector into first to third light;
A first filter for inputting the second light and selectively transmitting light having an output light wavelength of the first reference light source;
A second filter that receives the third light and selectively transmits light having an output light wavelength of the second reference light source;
The control signal, the output of the first filter, and the wavelength of the first reference light source; and the control signal, the output of the second filter, and the relationship between the wavelength of the second reference light source, the wavelength A wavelength selection module comprising: a control unit that adjusts a relationship between a control signal supplied to the selection unit and a selected wavelength.
6. The wavelength selection module according to claim 3, wherein the control unit is configured to continuously select light selectively transmitted by the first or second filter by the wavelength selection unit. 7. A wavelength selection module for controlling a control signal.
The wavelength selection module according to claim 3, wherein the control unit suppresses an output of the control signal corresponding to light selectively transmitted by the first or second filter, A wavelength selection module for suppressing output of a wavelength of light selectively transmitted by the first or second filter to the first light.
The wavelength selection module according to claim 3, wherein:
The wavelength selection module according to claim 1, further comprising a third filter that receives the first light and attenuates a wavelength of the light selectively transmitted by the first or second filter.

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