JP4694521B2 - Optical wavelength converter - Google Patents

Description

  The present invention relates to an all-optical processing type optical wavelength converter used for outputting a wavelength-multiplexed optical signal to an arbitrary path in an optical cross-connect node of an optical communication network, and an optical wavelength conversion device including the same. Is.

A conventional optical wavelength converter is formed on a semiconductor substrate (hereinafter referred to as an “InP substrate”) formed of a compound crystal of indium and phosphorus, and has a first semiconductor optical amplifier (Semiconductor Optical Optical) having a length of 2.4 mm. A transparent waveguide that forms an interferometer by connecting the first SOA and the second SOA in parallel to each other, the first SOA, and the second SOA formed in parallel with the first SOA (hereinafter referred to as “SOA”). , A probe light input terminal connected to both the first SOA and the second SOA by a transparent waveguide, and connected to both the first SOA and the second SOA by a transparent waveguide to the counter electrode of the probe light input terminal An optical output terminal located; a signal light input terminal connected to the first SOA by a transparent waveguide; a first phase adjustment waveguide fabricated by evaporating an electrode on a part of the transparent waveguide; and a transparent waveguide one Depositing an electrode having a second phase adjustment waveguides have been fabricated on.
Then, probe light is incident from the probe light input terminal, signal light is incident from the signal light input terminal, and wavelength-converted light is emitted from the light output terminal.

When signal light having a wavelength of 1.53 μm and a power of about 1 mW is introduced into the optical wavelength converter from the signal light input terminal, it travels through the transparent waveguide and is amplified by the first SOA. At this time, since the carrier density of the first SOA is modulated in synchronization with the increase and decrease of the signal light power, the gain and the refractive index also increase and decrease in synchronization with the signal light.
On the other hand, when probe light having a wavelength different from that of signal light, for example, 1.55 μm and power of about 1 mW is incident from the probe light input terminal, it is branched on the propagation optical path of the transparent waveguide, and the first SOA and the second Each is amplified by SOA. Since the first SOA is subjected to gain and refractive index modulation in synchronization with the signal light, the amplitude and phase of the probe light output from the first SOA are subjected to this modulation.

  If cross-gain modulation (hereinafter referred to as “XGM”) is used as amplitude modulation, and cross-phase modulation (hereinafter referred to as “XPM”) is used as phase modulation, XPM is received. The probe light having a wavelength of 1.55 μm is output from the output light terminal as wavelength converted light having a high extinction ratio due to a synergistic effect with XGM after the phase modulation is converted into intensity modulation by the action of the interferometer.

  Here, since the carrier density and gain of the first SOA decrease as the signal light increases, it is necessary to pay attention to the fact that the wavelength converted light by XGM is inverted in polarity. However, since the optical wavelength converter of the interferometer configuration can reverse the ON / OFF polarity of the light depending on the phase of the interference, the phase adjustment of the interferometer is performed in the Mach-Zehnder interferometer type using both XGM and XPM. The polarity of the wavelength-converted light output by can take both inversion and non-inversion.

For the purpose of adjusting the phase of such an interferometer, a first phase adjustment waveguide and a second phase adjustment waveguide are formed. These phase adjusting waveguides change the refractive index of the waveguide minutely by forming an electrode in the vicinity of the transparent waveguide and injecting a current. Since the first and second phase adjustment waveguides are for adjusting the phase difference between both arms of the interferometer, only one of them is required if a phase adjustment waveguide that ideally changes only the phase can be produced. Actually, the optical loss in the waveguide also increases / decreases due to the increasing / decreasing carrier. Therefore, in order to cancel the influence of the loss of the phase adjusting waveguide, the phase is changed by slightly changing the current on one side while flowing a bias current substantially equal to both (For example, refer nonpatent literature 1).

Yasunori Miyazaki, outside seven, "Polarization-Intensitive SOA-MZI Monolithic All-Optical Wavelength Converter for Full C-band 40Gbps-NRZ Operation", Proceedings of 32nd European Coference on Optical Communication (ECOC2006), vol6, paperTh3.4.2

  However, in the conventional optical wavelength converter, the phase-modulated light is converted into intensity-modulated light by an interferometer and output, so that the allowable range of input signal power is ± 0.5 dB centered on the optimum operating point. There is only a degree. Therefore, there are problems such as waveform deterioration due to burst signal level fluctuation, polarization dependence of output waveform, increased power consumption due to constant SOA temperature adjustment, and concerns over long-term reliability of phase adjustment values.

  SUMMARY OF THE INVENTION An object of the present invention is to monitor an optimum operating point without affecting a main signal, adjust the output signal-to-noise ratio to be maximized, and simplify a low-cost optical wavelength converter of an optical system and an optical device including the same. A wavelength converter is provided.

The optical wavelength conversion device according to the invention outputs the two probe light passed through the two arms inserted respectively a semiconductor optical amplifier as the wave to the main signal,
Each of the two probe lights that have passed through the semiconductor optical amplifier is demultiplexed into two, and one of the probe light that has been demultiplexed through the semiconductor optical amplifier and the other of the semiconductor optical amplifier is separated. One of the probe lights that have been multiplexed is combined and output as the main signal, and the other probe light that has been demultiplexed through the one semiconductor optical amplifier and the other semiconductor optical amplifier are demultiplexed. The other probe light is multiplexed to generate monitor light, and the optical path lengths through which the two probe lights pass through the two arms before being combined are input to the semiconductor optical amplifier. Adjusts the phase of the probe light adjusting means that adjusts the power of the previous probe light, the photodiode that converts the monitor light into current, and the other probe light that passes through the other semiconductor optical amplifier and is demultiplexed. An optical wavelength converter having a first phase adjusting unit that performs a phase reference current flow through the first phase adjusting unit, a modulation degree of the phase reference current is obtained from a PD current, and the modulation degree is a predetermined value And a control circuit for adjusting the probe light adjusting means .

  The effect of the optical wavelength converter according to the present invention is that the terminal for monitoring the interference state can be provided without affecting the main signal, and the optimum operating point can be monitored.

Embodiment 1 FIG.
FIG. 1 is a block diagram of an optical wavelength conversion device according to Embodiment 1 of the present invention. FIG. 2 is a circuit diagram of a control circuit according to the first embodiment of the present invention. The thick line in FIG. 1 represents the waveguide.
As shown in FIG. 1, the optical wavelength converter according to Embodiment 1 of the present invention includes an optical wavelength converter 2 formed on an InP substrate 1 and a control circuit 3 that controls the optical wavelength converter 2.
The optical wavelength converter 2 according to Embodiment 1 of the present invention includes a first SOA 4 having a length of 2.4 mm, a second SOA 5 formed in parallel with the first SOA 4, and a probe light input into which probe light is incident. A terminal 6; a signal light input terminal 7 into which signal light is incident; a light output terminal 8 from which wavelength-converted light is emitted; a photodiode (hereinafter referred to as “PD”) 9 that converts light into a current; It has a front SOA 10 as probe light adjusting means for increasing and decreasing.

  In addition, the optical wavelength converter 2 according to Embodiment 1 has one end connected to the probe light input terminal 6 and the other end connected to the front SOA 10, and one end connected to the front SOA 10. One end of each of the two waveguides 14a and 14b branched in the middle is connected to the first SOA 4 and the second SOA 5, respectively, and one end is connected to the signal light input terminal 7. The other end of the second transparent waveguide 14 is branched to the third transparent waveguide 15 coupled to the waveguide 14a connected to the first SOA 4, and the other end is connected to the first SOA 4. One end of the two waveguides 16a and 16b branched in the middle is connected to the optical output terminal 8 and the PD 9 respectively, and the other end is connected to the second SOA 5 and branched in the middle. Two waveguides 17a, 1 b One end of having two waveguides 16a fifth transparent waveguide 17, are respectively coupled to 16b which are branched in the fourth transparent waveguide 16.

  In addition, the optical wavelength converter 2 according to the first embodiment includes the first phase adjustment waveguide 20 and the second phase adjustment waveguide 20 that are formed in the waveguides 16 a and 16 b after the fourth transparent waveguide 16 is branched. A third phase adjusting waveguide 22 and a fourth phase adjusting waveguide 23 as phase adjusting means formed in the branched waveguides 17 a and 17 b of the phase adjusting waveguide 21 and the fifth transparent waveguide 17. Have.

  In addition, the optical wavelength converter 2 according to the first embodiment includes the first electrode 26 electrically connected to the front SOA 10 and the second electrode electrically connected to the third phase adjustment waveguide 22. 27, a third electrode 28 electrically connected to the fourth phase adjusting waveguide 23, and a fourth electrode 29 electrically connected to the PD9.

Then, from the branch point where the second transparent waveguide 14 is branched, the branched one waveguide 16a of the fourth transparent waveguide 16 passes through the waveguide 14a and the first SOA 4 to the fifth One arm of the first interferometer is formed up to a coupling point where the transparent waveguide 17 is coupled to one of the branched waveguides 17a.
Also, from the branch point where the second transparent waveguide 14 is branched, the branched one waveguide 17a of the fifth transparent waveguide 17 via the waveguide 14b and the second SOA 5 is the fourth The other arm of the first interferometer is formed up to the coupling point where the transparent waveguide 16 is coupled to one branched waveguide 16a.

Also, from the branch point where the second transparent waveguide 14 branches, the other branched waveguide 16b of the fourth transparent waveguide 16 via the waveguide 14a and the first SOA 4 is the fifth. One arm of the second interferometer is formed up to the coupling point where the transparent waveguide 17 is coupled to the other branched waveguide 17b.
Also, from the branching point where the second transparent waveguide 14 is branched, the other branched waveguide 17b of the fifth transparent waveguide 17 is connected to the fourth via the waveguide 14b and the second SOA 5. The other arm of the second interferometer is configured up to the coupling point where the transparent waveguide 16 is coupled to the other branched waveguide 16b.

The first to fourth phase adjusting waveguides 20 to 23 are produced by depositing electrodes on a part of the transparent waveguide. Then, by injecting a predetermined current into the electrode, the refractive index of the waveguide is changed, and the phase of light passing therethrough is adjusted.
Probe light is incident on the probe light input terminal 6, signal light is incident on the signal light input terminal 7, and wavelength-converted light is emitted from the light output terminal 8.

  As shown in FIG. 2, the control circuit 3 according to Embodiment 1 of the present invention includes a signal source 31 that outputs a 1 MHz dither signal as a phase reference current, a first current source 32 that outputs a phase adjustment current, and a modulation. Based on the second current source 33 that outputs the degree adjustment current, the filter 34 that passes only the 1 MHz AC component of the PD current, the inductor 35 that passes the DC component of the PD current, the 1 MHz AC component of the PD current and the phase reference current Phase control means 36 for obtaining a phase adjustment signal, modulation for calculating the modulation degree of the phase reference current from the direct current component and the 1 MHz alternating current component of the PD current, and adjusting the front SOA 10 so that the modulation degree becomes a predetermined value, for example, 25% Modulation degree adjusting means 37 for obtaining a degree adjustment signal is provided.

  The signal source 31 is connected to the third electrode 28, the first current source 32 is connected to the second electrode 27, the second current source 33 is connected to the first electrode 26, and the filter 34 and the inductor 35 are connected to the fourth electrode 29. It is connected to the.

Next, the operation of the optical wavelength converter 2 according to Embodiment 1 will be described.
First, the operation of the first interferometer in which wavelength-converted light is output from the light output terminal 8 will be described.
When signal light having a wavelength of 1.53 μm and a power of about 1 mW is incident on the signal light input terminal 7, it travels from the third transparent waveguide 15 through the waveguide 14 a and is amplified by the first SOA 4. At this time, since the carrier density of the first SOA 4 is modulated in synchronization with the increase or decrease of the signal light power, the gain and the refractive index also increase or decrease in synchronization with the signal light.
On the other hand, after the probe light having a wavelength different from that of the signal light, for example, 1.55 μm and power of about 1 mW is incident from the probe light input terminal 6 and is subjected to a predetermined amount of amplification by the front SOA 10, The light is demultiplexed by the waveguide 14 and amplified by the first SOA 4 and the second SOA 5 respectively.

  Since the first SOA 4 is modulated in gain and refractive index in synchronization with the signal light, the probe light is modulated, and the probe light output from the first SOA 4 is modulated in amplitude and phase. The probe light having a wavelength of 1.55 μm subjected to XPM is emitted from the optical output terminal 8 as wavelength converted light having a high extinction ratio due to a synergistic effect with XGM after the phase modulation is converted into intensity modulation by the action of the interferometer. The

  Here, when the signal light increases, the carrier density and gain of the first SOA 4 decrease, so that the polarity of the wavelength converted light by XGM is inverted. However, in the optical wavelength converter of the interferometer configuration, the ON / OFF polarity of light can be reversed depending on the state of the interfering phase. Therefore, in the optical wavelength converter using both XGM and XPM, the phase adjustment of the interferometer The polarity of the wavelength-converted light output by can take both inversion and non-inversion.

  For the purpose of adjusting the phase of such an interferometer, a first phase adjustment waveguide 20 and a third phase adjustment waveguide 22 are formed. Since the first and third phase adjustment waveguides 20 and 22 are for adjusting the phase difference between both arms of the first interferometer, if a phase adjustment waveguide that changes only the phase ideally can be produced, Only one of the phase adjustment waveguides is required. However, since the optical loss in the waveguide also increases / decreases due to the increasing / decreasing carrier, in order to cancel the influence of the loss of the phase adjustment waveguide, an approximately equal bias current is applied to both. While flowing, the phase is adjusted by minutely changing one of the currents.

Since the wavelength converted light contains 1.53 μm signal light in addition to 1.55 μm wavelength converted light, it is used after removing light other than wavelength converted light by a bandpass filter not shown. To do.
The first interferometer operates as described above. However, in order to operate optimally, the output amplitude of the probe light output from the first SOA 4 and the second SOA 5 is made equal to improve the extinction ratio. It is necessary to let Therefore, the front SOA 10 is installed for the purpose of increasing or decreasing the power of the probe light following the power of the signal light.
Further, since there is an optimum state not only in the output amplitude of the probe light output from the first SOA 4 and the second SOA 5, but also in the phase relationship, the outputs from the first SOA 4 and the second SOA 5 are It is necessary to adjust with the 1st phase adjustment waveguide 20 and the 3rd phase adjustment waveguide 22, respectively.

Next, the operation of the second interferometer in which wavelength converted light is input to the PD 9 will be described. Since the operations up to the output terminals of the first SOA 4 and the second SOA 5 are the same as the operation of the first interferometer, the description thereof will be omitted and the subsequent operations will be described.
The probe light output from the first SOA 4 passes through the other branched waveguide 16 b of the fourth transparent waveguide 16, and the probe light output from the second SOA 5 branches from the fifth transparent waveguide 17. The other light passes through the other waveguide 17b and is combined. Then, the combined wavelength converted light is input to the PD 9 as monitor light.

The PD 9 outputs a current proportional to the amplitude of the wavelength converted light. Then, by changing the current flowing through the fourth phase adjusting waveguide 23, the operating point of the second interferometer is dithered, and the signal light and the probe propagated while receiving the amplification action in the optical wavelength converter 2 The proportion of light can be monitored.
Then, the optimum operating state of the optical wavelength converter is obtained by applying feedback to the front SOA 10 and the third phase adjustment waveguide 22 so as to keep the modulation degree and the interference phase obtained from the monitor signal at the optimum modulation degree and interference phase. Can keep.

Next, the operation of the control circuit according to the first embodiment will be described.
When a phase reference current is passed from the signal source 31 to the fourth phase adjustment waveguide 23, the phase state of the second interferometer changes, and therefore the output current of the PD 9 proportional to the optical output after interference also changes. . FIG. 3 shows the relationship between the phase reference current flowing through the fourth phase adjustment waveguide 23 and the PD current at this time.
In FIG. 3, the horizontal axis is the phase reference current, the vertical first axis is the PD current, the vertical second axis is the wavelength-converted optical power, and the signal light input is 0.6 mW. FIG. 3 shows that the PD current and the wavelength-converted light power are synchronized with respect to the phase reference current, and the wavelength-converted light power becomes almost zero when the PD current becomes a minimum value.
FIG. 4 shows the relationship between the phase reference current, the PD current, and the wavelength-converted optical power when the signal light input is 1.2 mW.

By applying a 1 MHz dither signal to the fourth phase adjustment waveguide 23 and measuring a 1 MHz AC component and a DC component of the PD current extracted from the fourth electrode 29, the degree of modulation is monitored, and the SOA SOA 10 is monitored. adjusting the modulation adjusting current I ₁ flowing.
Further, by detecting synchronously the 1 MHz output signal of the PD current with reference to the 1 MHz signal input to the fourth phase adjustment waveguide 23, the relative phase change is detected with high accuracy, and the third phase adjustment is performed. Feedback is applied to the phase adjustment current I ₂ flowing through the waveguide 22.

  Thus, the present inventor has experimentally confirmed that the optimum operating point for the amplitude of the optical wavelength converter 2 is when the degree of modulation of the PD current is about 25% regardless of the input power of the signal light. Yes. Using this relationship, the phase reference current flowing through the fourth phase adjustment waveguide 23 is changed, and the PD current flowing from the fourth electrode 29 is measured to obtain the modulation degree of the output light. If the amplitude of the probe light is adjusted by the front SOA 10 so as to be%, the optimum amplitude relationship can always be maintained regardless of the power of the signal light.

In addition, since it is possible to know the optimum operating point of the phase reference current from the relationship between the phase reference current and the wavelength-converted optical power shown in FIGS. 3 and 4, the fourth phase adjustment is performed so that the PD current becomes constant. The phase relationship of the first interferometer can be obtained from the optical output terminal 8 by adjusting the phase reference current flowing through the waveguide 23 and flowing the same phase adjustment current as this phase reference current through the third phase adjustment waveguide 22. It is possible to maintain the optimum operating state for the wavelength converted light.
The optimum operating state is generally a state where the extinction ratio is maximized. At this time, the phase reference current that is changed to measure the modulation factor and interferometer phase relationship only affects the monitor-specific interferometer that is output in parallel with the main signal path, so the main signal is not disturbed. There is an advantage that the optimum value of the modulation degree can be adjusted and the phase of the interferometer can be adjusted.

The optical wavelength converter 2 according to the first embodiment of the present invention can have a terminal for monitoring the interference state without affecting the main signal, and can monitor the optimum operating point.
Further, by adjusting the input power of the probe light with the front SOA 10, the ratio of the probe light and the signal light can be adjusted to a desired value without adding a cause of noise increase such as loss on the signal input side, Adjustment can be made to always maximize the output signal-to-noise ratio.
Further, by converting the monitor light into current by the PD 9, the optical system can be simplified and can be provided at low cost.

The optical wavelength conversion device according to the first embodiment of the present invention is the optimum operating point of the interference operation caused by the increase or decrease of the input power of the signal light, the change of the input polarization of the signal light, or the change of the SOA gain due to the change of the environmental temperature. By monitoring the deviation from and adjusting the probe light power to keep the optimum modulation degree at all times, the Uncooled operation of the optical wavelength converter becomes possible, the operation is not affected by the polarization state of the input signal, In addition, the input dynamic range of the signal light power can be widened.
In addition, long-term reliability can be ensured by measuring the optimum phase shift during the long-term operation of the SOA with a monitor system and applying feedback to the interference operation on the main signal side.

Embodiment 2. FIG.
FIG. 5 is a block diagram of an optical wavelength converter according to Embodiment 2 of the present invention.
As shown in FIG. 5, the optical wavelength converter 2B according to the second embodiment of the present invention is a variable optical attenuation waveguide as a probe light adjusting means instead of the front SOA 10 of the optical wavelength converter 2 according to the first embodiment. (Hereinafter referred to as “VOA”) 41 is different, and the others are the same, so the same reference numerals are given to the same parts and the description is omitted.
The VOA 41 according to the second embodiment uses an effect of absorbing light by forming an electrode in a waveguide and injecting electrons by passing a current. It is also possible to use a waveguide using the Franz Keldish effect of an absorption optical semiconductor whose loss changes by applying an electric field.

  By having the VOA 41 for adjusting the power of the probe light in this way, the ratio of the probe light and the signal light can be adjusted to a desired value without adding a cause of noise increase such as loss on the signal input side. Adjustments can be made to maximize the output signal-to-noise ratio.

Embodiment 3 FIG.
FIG. 6 is a block diagram of an optical wavelength converter according to Embodiment 3 of the present invention.
The optical wavelength converter 2C according to Embodiment 3 of the present invention is different from the optical wavelength converter 2 according to Embodiment 1 in the first interferometer and the second interferometer as shown in FIG. Since it is the same, the same code | symbol is attached | subjected to the same part and description is abbreviate | omitted.
The first interferometer according to the third embodiment is different from the first interferometer according to the first embodiment in the relationship between the lengths of the two arms, and the other portions are the same. The description is omitted. The length of the first arm of the first interferometer according to the third embodiment is the same as the length of the second arm of the first interferometer. That is, the length of one waveguide 17a of the fifth transparent waveguide 17 is reduced by forming the branched one waveguide 16a of the fourth transparent waveguide 16 instead of a straight line. Can be equal.

Further, the second interferometer according to the third embodiment is different from the second interferometer according to the first embodiment in the relationship between the lengths of the two arms, and the other portions are the same. The description is omitted. The length of the second arm of the second interferometer according to the third embodiment is the same as the length of the first arm of the second interferometer. That is, by forming the other branched waveguide 17b of the fifth transparent waveguide 17 in a detour instead of a straight line, the length of the other waveguide 16b of the fourth transparent waveguide 16 is increased. Can be equal.
The first interferometer arm and the second interferometer arm are formed to have the same length.

  By making both arms of the interferometer have the same length in this way, the two interferometers have been operated in the same manner. Therefore, the fourth phase adjustment waveguide 23 for adjusting the phase of the monitor light and the main signal light By causing substantially the same current to flow through the third phase adjustment waveguide 22 for adjusting the phase, the phase conditions in the operations of both interferometers can be made equal, and the phase adjustment of the interferometers can be simplified.

Embodiment 4 FIG.
FIG. 7 is a block diagram of an optical wavelength converter according to Embodiment 4 of the present invention.
As shown in FIG. 7, the optical wavelength converter 2D according to the fourth embodiment of the present invention is different in the installation location of the optical wavelength converter 2 and the front SOA 10 according to the first embodiment, and is otherwise the same. Similar parts are denoted by the same reference numerals, and description thereof is omitted.
In the optical wavelength converter 2D according to the fourth embodiment, the front SOA 10 is inserted into the third transparent waveguide 15.

  By adjusting the power of the signal light by the front SOA 10 in this way, the relative power ratio between the signal light and the probe light is changed and a desired modulation degree can be obtained, so that the output SN ratio is always maximized. Can be adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the optical wavelength converter by Embodiment 1 of this invention. It is a circuit diagram of the control circuit by Embodiment 1 of this invention. It is a graph which shows the dependence with respect to the phase reference current of PD current and signal light when wavelength of signal light is 0.6 mW. It is a graph which shows the dependence with respect to the phase reference current of PD current and signal light when the signal light power is 1.2 mW. It is a block diagram of the optical wavelength converter by Embodiment 2 of this invention. It is a block diagram of the optical wavelength converter by Embodiment 3 of this invention. It is a block diagram of the optical wavelength converter by Embodiment 4 of this invention.

Explanation of symbols

  1 InP substrate, 2, 2B, 2C, 2D Optical wavelength converter, 3 Control circuit, 4, 5 Semiconductor optical amplifier (SOA), 6 Probe light input terminal, 7 Signal light input terminal, 8 Light output terminal, 9 Photo diode (PD), 10 pre-SOA, 13, 14, 15, 16, 17 transparent waveguide, 14a, 14b, 16a, 16b, 17a, 17b waveguide, 20, 21, 22, 23 phase adjustment waveguide, 26, 27, 28, 29 Electrode, 31 Signal source, 32, 33 Current source, 34 Filter, 35 Inductor, 36 Phase control means, 37 Modulation degree adjustment means, 41 Variable optical attenuation waveguide (VOA).

Claims (2)

The two probe lights that have passed through the two arms into which the semiconductor optical amplifiers are inserted are combined and output as a main signal,
Each of the two probe lights that have passed through the semiconductor optical amplifier is demultiplexed into two, and one of the probe light that has been demultiplexed through the semiconductor optical amplifier and the other of the semiconductor optical amplifier is separated. One of the probe lights that have been multiplexed is combined and output as the main signal, and the other probe light that has been demultiplexed through the one semiconductor optical amplifier and the other semiconductor optical amplifier are demultiplexed. The other probe light is combined to generate monitor light,
The optical path lengths through which the two probe lights pass before passing through the two arms and being combined are equal,
Probe light adjusting means for adjusting the power of the probe light before being input to the semiconductor optical amplifier;
A photodiode for converting the monitor light into a current;
First phase adjusting means for adjusting the phase of the other probe light demultiplexed after passing through the other semiconductor optical amplifier ;
An optical wavelength converter having:
A control circuit for supplying a phase reference current to the first phase adjustment unit, obtaining a modulation degree of the phase reference current from a PD current, and adjusting the probe light adjustment unit so that the modulation degree becomes a predetermined value;
An optical wavelength conversion device comprising: The optical wavelength converter has a second phase adjusting means for adjusting the phase of one of the probe lights that has been demultiplexed through the other semiconductor optical amplifier,
2. The control circuit according to claim 1, wherein the same phase adjustment current as a phase reference current that causes an optimum operation state of the interferometer that outputs the monitor light of the optical wavelength converter flows to the second phase adjustment means. 2. The optical wavelength converter according to 2 .

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