JP5030205B2 - Wavelength stabilization apparatus and wavelength stabilization method - Google Patents

Description

  The present invention relates to a technique for stabilizing the wavelength of an optical signal in optical communication, and particularly to a technique for stabilizing the wavelength of an optical signal in wavelength division multiplexing communication.

  In recent years, construction of a large-capacity optical communication system is progressing due to an increase in data communication traffic including the Internet. Under such circumstances, wavelength division multiplexing (WDM) technology has been actively introduced. This technology can contribute not only to an increase in the capacity of the network but also to the flexible construction of the network because different services and users can be assigned for each wavelength. The communication capacity depends on the number of wavelengths that can be used, and the number of wavelengths is limited by the band of an optical device such as a wavelength multiplexer / demultiplexer to be used. Therefore, in order to increase the communication capacity, it is necessary to increase the density of wavelength intervals. Therefore, a technique for stabilizing the wavelength of the signal light is required. For example, techniques disclosed in Patent Document 1 and Patent Document 2 have been proposed.

  Patent Documents 3 and 4 disclose wavelength stabilization devices using wavelength transmission means in which a Mach-Zehnder interferometer circuit (MZI circuit) that dithers wavelength transmission characteristics at a predetermined frequency and an arrayed waveguide diffraction grating (AWG). Is disclosed.

JP 11-31859 A JP 2003-258373 A JP-A-8-51411 JP-A-9-261181

  In patent document 1, in order to stabilize the wavelength of signal light, the wavelength locker is attached for every light source. However, since the wavelength locker requires many expensive optical components such as an optical filter, there has been a problem that the cost of the transmitter is significantly increased. Therefore, Patent Document 2 proposes a wavelength stabilization method that does not use a wavelength locker.

  However, the technique found in Patent Document 2 has a problem in that the control signal for stabilizing the wavelength and the data signal component overlap on the spectrum, and therefore the signal-to-noise ratio (SNR) of the control signal deteriorates. . Further, according to the technique using the pilot signal of Patent Document 2, the configuration of the optical transmitter and the optical receiver is complicated, and there is a problem that the cost is increased. Further, in the configuration of Patent Document 2, it is essential to use an intensity modulator on the optical transmitter side, and there is a problem that it cannot be applied to an optical transmitter that directly modulates a semiconductor laser with a data signal.

  Patent Documents 3 and 4 propose a configuration in which one AWG is connected to one output port of the MZI circuit. With the transmission characteristic to one output port of the MZI circuit, the -3 dB transmission bandwidth cannot exceed half of the channel interval of the wavelength multiplexed signal. Therefore, since this configuration has a narrow transmission band, even if it can be used to generate a signal for controlling the wavelength, it cannot be used as an optical demultiplexer for wavelength-multiplexed signal light.

  Patent Document 4 proposes a configuration in which two AWGs are connected to each of two output ports of an MZI circuit. In this configuration, since the wavelength deviation is detected by comparing the outputs of the two AWGs, the signal wavelength is separated from the transmission center wavelength of the MZI circuit and the AWG. Therefore, this configuration cannot be used as an optical demultiplexer for wavelength-multiplexed signal light.

  As described above, Patent Documents 3 and 4 require a configuration in which signal light for wavelength deviation detection and signal light for transmitting data are separated in advance using an optical coupler. For this reason, there was a problem that it was complicated and had many components.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wavelength stabilization device and a wavelength stabilization method capable of stabilizing the wavelength with a simple configuration. .

In order to achieve the above object, the present invention provides a wavelength transmission means for transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, Dithering means for dithering the wavelength transmission characteristic at a predetermined frequency, photoelectric conversion means for converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal, and conversion by the photoelectric conversion means Filter means for extracting the signal of the predetermined frequency from the electrical signal, and generating a signal for controlling the wavelength of the optical signal on the transmission side from the phase component and amplitude component of the extracted signal, and feeding back to the transmission side and a signal generating means for said signal generating means, as described above penalty loss budget for the optical signal is allowed to the optical fiber transmission path propagated is optimal light And generating a signal for controlling the wavelength of No..

According to a second aspect of the present invention, there is provided a wavelength transmission means for transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, and a dither for dithering the wavelength transmission characteristic of the reception side with a predetermined frequency. A ring means, a photoelectric conversion means for converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal, and a signal having the predetermined frequency is extracted from the electrical signal converted by the photoelectric conversion means. Filter means; and a signal generation means for generating a signal for controlling the wavelength of the optical signal on the transmission side from the phase component and amplitude component of the extracted signal, and feeding back to the transmission side,
The wavelength transmitting means is an arrayed waveguide diffraction grating that transmits an optical signal in which a plurality of wavelengths are multiplexed with a predetermined wavelength transmission characteristic according to the wavelength, and the dithering means is configured to transmit the optical signal of the arrayed waveguide diffraction grating. Dithering wavelength transmission characteristics at a predetermined frequency, the photoelectric conversion means converts optical signals of a plurality of wavelengths that have passed through the dithered wavelength transmission characteristics into a plurality of electrical signals, respectively, the filter means and The signal generating means is configured to share the plurality of electric signals via a switch.

According to a third aspect of the present invention, there is provided a wavelength transmission means for transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, and a dither for dithering the wavelength transmission characteristic of the reception side with a predetermined frequency. A ring means, a photoelectric conversion means for converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal, and a signal having the predetermined frequency is extracted from the electrical signal converted by the photoelectric conversion means. A filter means; and a signal generation means for generating a signal for controlling the wavelength of the optical signal on the transmission side from the phase component and the amplitude component of the extracted signal and feeding back to the transmission side, and the wavelength transmission means A Mach-Zehnder interferometer circuit having a first output and a second output; a first arrayed waveguide grating connected to the first output; and a second output connected to the first output. And the Mach-Zehnder interferometer circuit converts an optical signal in which a plurality of wavelengths are multiplexed into an odd-numbered wavelength group and an even-numbered wavelength group according to the wavelength. The odd-numbered wavelength group optical signals are output via the first output, and the even-numbered wavelength group optical signals are output via the second output, respectively. The first arrayed waveguide diffraction grating transmits the optical signal of the transmitted odd-numbered wavelength group with a second wavelength transmission characteristic, and transmits the second arrayed waveguide diffraction grating. Transmits the transmitted optical signal of the even-numbered wavelength group with a third wavelength transmission characteristic, and the dithering means sets the first wavelength transmission characteristic of the Mach-Zehnder interferometer circuit to a predetermined frequency. Characterized in that it is configured to dither.

According to a fourth aspect of the present invention, there is provided a wavelength transmission means for transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, and a dither for dithering the wavelength transmission characteristic of the reception side with a predetermined frequency. A ring means, a photoelectric conversion means for converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal, and a signal having the predetermined frequency is extracted from the electrical signal converted by the photoelectric conversion means. A filter means; and a signal generation means for generating a signal for controlling the wavelength of the optical signal on the transmission side from the phase component and the amplitude component of the extracted signal and feeding back to the transmission side, and the wavelength transmission means Is an arrayed waveguide grating that transmits an optical signal in which a plurality of wavelengths are multiplexed with a predetermined wavelength transmission characteristic according to the wavelength, and the dithering means includes the array dithering means. The waveguide grating conductive thin film heater of the wavelength transmission characteristic is formed in the arrayed waveguide surface, characterized in that it is configured to dither at a predetermined frequency. Further, the invention according to claim 5 is the wavelength stabilization device according to any one of claims 1 to 4 , wherein the signal generation means sets the wavelength of the optical signal to a center wavelength of the predetermined wavelength transmission characteristic. A signal for controlling the wavelength of the optical signal so as to match is generated.

The invention according to claim 6 is a step of transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, a step of dithering the wavelength transmission characteristic of the reception side with a predetermined frequency, Converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electric signal; extracting a signal of the predetermined frequency from the converted electric signal; and a phase component of the extracted signal; Generating a signal for controlling the wavelength of the optical signal on the transmitting side from the amplitude component, and feeding back to the transmitting side, and the generating step is allowed for an optical fiber transmission path through which the optical signal has propagated. Generating a signal for controlling the wavelength of the optical signal so as to optimize the penalty of the loss budget.

The invention according to claim 7 is a step of transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, a step of dithering the wavelength transmission characteristic of the reception side with a predetermined frequency, Converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal;
Extracting the signal of the predetermined frequency from the converted electrical signal; generating a signal for controlling the wavelength of the optical signal on the transmission side from the phase component and the amplitude component of the extracted signal; And the step of transmitting transmits an optical signal in which a plurality of wavelengths are multiplexed with a predetermined wavelength transmission characteristic according to the wavelength, and the dithering includes the wavelength transmission characteristic Dithering at a predetermined frequency and converting the optical signal having a plurality of wavelengths transmitted through the dithered wavelength transmission characteristics into a plurality of electrical signals, and switching the plurality of electrical signals. ,
The extracting step and the generating step are executed.

The invention according to claim 8 is a step of transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, a step of dithering the wavelength transmission characteristic of the reception side with a predetermined frequency, Converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal;
Extracting the signal of the predetermined frequency from the converted electrical signal; generating a signal for controlling the wavelength of the optical signal on the transmission side from the phase component and the amplitude component of the extracted signal; And the step of transmitting the optical signal in which a plurality of wavelengths are multiplexed is divided into an odd-numbered wavelength group and an even-numbered wavelength group according to the wavelength. Transmitting the optical signal with a first wavelength transmission characteristic; demultiplexing the transmitted optical signal of the odd-numbered wavelength group for each wavelength and transmitting the optical signal with a second wavelength transmission characteristic; Further comprising the step of demultiplexing the transmitted optical signals of the even-numbered wavelength groups for each wavelength and transmitting them with a third wavelength transmission characteristic, respectively. That step is characterized by dithering the first wavelength transmission characteristics.

The invention according to claim 9 is a step of transmitting an optical signal from the transmission side with a predetermined wavelength transmission characteristic on the reception side, a step of dithering the wavelength transmission characteristic of the reception side with a predetermined frequency, Converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal;
Extracting the signal of the predetermined frequency from the converted electrical signal; generating a signal for controlling the wavelength of the optical signal on the transmission side from the phase component and the amplitude component of the extracted signal; And transmitting the optical signal having a plurality of wavelengths multiplexed by an arrayed waveguide diffraction grating with a predetermined wavelength transmission characteristic according to the wavelength, and dithering the optical signal. Is characterized in that the wavelength transmission characteristic of the arrayed waveguide diffraction grating is dithered at a predetermined frequency by a conductive thin film heater formed in the arrayed waveguide. Further, the invention according to claim 10 is the wavelength stabilization method according to any one of claims 6 to 9 , wherein in the generating step, the wavelength of the optical signal is set to a center wavelength of the predetermined wavelength transmission characteristic. A signal for controlling the wavelength of the optical signal so as to match is generated.

  Hereinafter, a comparative example of the present invention will be described first, and then an embodiment of the present invention will be described.

(Comparative example)
FIG. 1 shows a wavelength multiplexing communication system that stabilizes the wavelength of signal light without using a wavelength locker as a comparative example of the present invention (see Patent Document 2). This communication system is wavelength-multiplexed with a plurality of optical transmitters 10-1 to 10 -N that output optical signals having different wavelengths, a wavelength multiplexer 20 that multiplexes these optical signals having different wavelengths and transmits them to an optical fiber. An optical fiber 30 through which the optical signal propagates, a wavelength demultiplexer 40 that demultiplexes the optical signal from the optical fiber according to the wavelength, and a plurality of optical receivers 50 that receive the demultiplexed optical signals. 1 to N. Each of the optical transmitters 10-1 to 10-N has the same configuration and function, and outputs optical signals having different wavelengths. Each of the optical receivers 50-1 to 50-N has the same configuration and function, and receives an optical signal having a wavelength of the corresponding optical transmitter.

  First, the configuration and operation of each part of the optical transmitter 10 in FIG. 1 will be described. The semiconductor laser 11 outputs continuous light having a predetermined wavelength set by the wavelength controller 12. The wavelength controller 12 outputs a wavelength setting signal to the semiconductor laser 11 according to a control signal from the corresponding optical receiver 50, and controls the wavelength of continuous light output from the semiconductor laser. As the semiconductor laser, a distributed feedback laser (DFB-LD: Distributed Feedback Laser-Diode) or a distributed Bragg reflection laser (DBR-LD: Distributed Bragg Reflector Laser-Diode) can be used. Since the output wavelengths of the DFB-LD and DBR-LD are set by temperature and injection current, respectively, the wavelength setting signal can be a signal suitable for each.

  The sine wave signal source 14 outputs a sine wave signal having a frequency f. The current source 15 supplies the semiconductor laser 11 with a current obtained by superimposing a predetermined bias value on the sine wave signal output from the sine wave signal source 14. The polarity inverter 16 inverts the polarity of the sine wave signal output from the sine wave signal source 14. The frequency divider 17 divides (or multiplies) the frequency f of the sine wave signal output from the sine wave signal source 14 by an integer, and a sine wave signal of frequency f ′ (hereinafter referred to as a pilot signal). Output. The adder 18 adds the sine wave signal whose polarity is inverted by the polarity inverter 16, the pilot signal generated by the frequency divider (or the multiplier), and the data signal transmitted to the corresponding optical receiver. .

  The intensity modulator 13 modulates the intensity of the continuous light from the semiconductor laser 11 with the signal obtained from the adder 18. At this time, adjustment is made so that the intensity modulation components of the sine wave signal from the semiconductor laser and the sine wave signal from the adder cancel each other.

  Next, the wavelength multiplexer 20 multiplexes optical signals of different wavelengths output from the optical transmitters 10-1 to 10-N, and generates a WDM signal. As the wavelength multiplexer, for example, an optical filter such as an arrayed waveguide grating (AWG) or a fiber grating can be used. Also, an optical coupler can be used instead of an optical filter. The WDM signal output from the wavelength multiplexer is transmitted to the wavelength demultiplexer 40 via the optical fiber 30. The wavelength demultiplexer 40 demultiplexes the WDM signal according to the wavelength and outputs the demultiplexed signal to each of the optical receivers 50-1 to 50 -N. For example, an arrayed waveguide diffraction grating (AWG) or a fiber grating can be used as the wavelength demultiplexer.

Next, the wavelength stabilization mechanism in this wavelength division multiplexing communication system will be described. The wavelength transmission characteristics from the input of the wavelength multiplexer 20 to the output of the wavelength demultiplexer 40 are shown in FIG. When the wavelength of the optical signal output from one of the optical transmitters is modulated with a sine wave with λ ₀ as the center, the time change of the wavelength of the optical signal is expressed by the following equation.

At this time, if the center wavelength λ _c of the wavelength transmission characteristic is shifted from the center wavelength λ ₀ of the optical signal, the wavelength change of the optical signal is converted into an intensity change as shown in FIG. This can be explained as follows. That is, the transmittance T from the wavelength multiplexer to the wavelength demultiplexer can be developed as shown in the following equation with the wavelength λ ₀ as the center.

When the optical signal power before being input to the wavelength multiplexer 20 and P _in, the optical signal power P _out after passing through the wavelength demultiplexer 40 is obtained by the following equation.

  The second term on the right side of the equation (3) is that after the transmission through the wavelength demultiplexer 40, an intensity modulation component having the same frequency as the time change of the wavelength of the equation (1) is generated in the optical signal, and its amplitude is the transmission characteristic. It shows that it is proportional to the first derivative of the transmittance T.

FIG. 2B shows a first-order differential component of the transmittance T of the transmission characteristics shown in FIG. If symmetrical with respect to the transmission characteristic transmission center wavelength lambda _c, 1-order derivative component of the transmittance in the transmission center wavelength lambda _c is zero. Therefore, the wavelength of the optical signal is modulated in advance with a sine wave, an intensity modulation component having the same frequency as that of the sine wave is detected after passing through the wavelength demultiplexer, and the center wavelength of the optical signal is set so that the amplitude becomes zero. By controlling λ ₀ , the center wavelength λ ₀ of the optical signal can be matched with the center wavelength λ _c of the transmission characteristics from the wavelength multiplexer to the wavelength demultiplexer.

  Next, signals in each block will be described with reference to FIG. 3 and FIG. When the signal waveform output from the sine wave signal source 14 is represented as shown in FIG. 3A, the intensity of the output light of the semiconductor laser 15 is modulated as shown in FIG. The wavelength is modulated as shown in FIG. In the following description, it is assumed that the wavelength changes to the longer wavelength side as the amount of current injected into the semiconductor laser increases, and there is no phase difference between the intensity modulation component and the wavelength modulation component.

  The waveform of the signal output from the polarity inverter 16 is obtained by inverting the waveform of FIG. 3A as shown in FIG. 3C, and is multiplexed with the data signal to be transmitted shown in FIG. , And input to the intensity modulator 13. When the intensity of the output light from the semiconductor laser is modulated by this signal, the intensity modulation component by the sine wave signal is canceled, and only the intensity modulation component by the data signal remains as shown in FIG. On the other hand, the modulation component of the wavelength is not affected by the intensity modulator, and the wavelength change given by the semiconductor laser remains as it is as shown in FIG. As described above, an optical signal whose intensity is modulated by the data signal and whose wavelength is modulated by the sine wave is obtained.

This optical signal is transmitted from the wavelength multiplexer 20 through the wavelength demultiplexer 40 via the optical fiber 30, and is affected by the transmission characteristics shown in FIG. Therefore, when the center wavelength λ ₀ of the optical signal is shifted from the transmission center wavelength λ _c of the transmission characteristics, the output of the wavelength demultiplexer 40 has the same frequency as the sine wave signal and the amplitude is proportional to the first derivative of the transmittance. An intensity modulation component (hereinafter referred to as a transmittance differential signal) is generated.

This optical signal is converted into an electrical signal by the photoelectric converter 51 of the optical receiver 50 and processed by the control signal detector 52. Specifically, a transmittance differential signal having a frequency f is extracted from the electrical signal converted by the photoelectric converter 51 through a bandpass filter (BPF1) 53. Further, a pilot signal having a frequency f ′ is extracted from the electric signal converted by the photoelectric converter 51 through a bandpass filter (BPF2) 54. The extracted pilot signal of frequency f ′ is then converted to a signal of the same frequency f as the transmittance differential signal by a multiplier (or a frequency divider), and multiplied by the transmittance differential signal of frequency f by a multiplier 54. The Here, when the phase of the transmittance differential signal is phase-locked so that it is in phase with the phase of the pilot signal when λ ₀ <λ _c , the phase is reversed when λ ₀ > λ _c . Further, the amplitude of the transmittance differential signal becomes zero when λ ₀ = λ _c and increases as the wavelength difference increases. Therefore, the signal multiplied by the multiplier 54 is a signal whose sign changes to plus or minus according to the magnitude relationship between λ ₀ and λ _c and whose amplitude changes according to the wavelength difference. A direct current component is extracted from this signal through a low-pass filter (LPF) 55, fed back to the wavelength controller 12 of the optical transmitter, and the output wavelength of the semiconductor laser 11 is controlled to thereby output the light output from the optical transmitter. The center wavelength λ _{0 of the} signal can be matched with the transmission center wavelength λ _c of the wavelength transmission characteristics from the wavelength multiplexer 20 to the wavelength demultiplexer 40.

  FIG. 5 shows the frequency spectrum of the data signal, transmittance differential signal, and pilot signal at the output of the photoelectric converter 51. FIG. 5 shows a case where the frequency f ′ of the sine wave signal source 14 is divided by half as the frequency f ′ of the pilot signal. As shown in the figure, the transmittance differential signal and the pilot signal are extracted by BPF1 and BPF2 of the control signal detector 52, respectively. However, since these signals are superimposed on the spectrum of the data signal, a part of the data signal becomes noise with respect to the extracted signal. In addition, circuit noise exists in the receiver. Therefore, noise also occurs in the control signal multiplied by these signals, and the accuracy of wavelength stabilization and the transmission distance capable of wavelength stabilization are limited. Note that the frequency of the sine wave signal source 14 can be set higher than the bit rate of the data signal by a multiplier to reduce superimposed noise, but this increases the spectrum of the optical signal, so that the WDM signal This is disadvantageous for higher density.

  Further, the above comparative example is based on the premise that the intensity modulator 13 is used in the optical transmitter, and is not applicable to a direct modulation type optical transmitter that directly modulates the bias current of the semiconductor laser with a data signal. Furthermore, according to the method using the pilot signal described above, the circuit configurations of the optical transmitter and the optical receiver are complicated.

(First embodiment)
FIG. 6 shows a wavelength division multiplexing communication system that stabilizes the wavelength of signal light according to the first embodiment of the present invention. As in the comparative example, this communication system includes a plurality of optical transmitters 110-1 to 110-N, a wavelength multiplexer 120, an optical fiber 130, a wavelength demultiplexer 140, and a plurality of optical receivers 150. And. The communication system according to the first embodiment of the present invention further includes a temperature setting unit 161 for setting the temperature of the wavelength demultiplexer 140, a sine wave signal source 162 for generating a sine wave signal having a frequency f, and a temperature setting unit 161. And an adder 163 for adding a signal from the sine wave signal source 162 and outputting a signal for controlling the transmission center wavelength of the wavelength demultiplexer 140.

  The optical transmitter 110 includes a semiconductor laser 111, a wavelength controller 112, and an intensity modulator 113. Similar to the comparative example, the semiconductor laser 111 is driven by a bias current and outputs continuous light having a predetermined wavelength. As the semiconductor laser, a distributed feedback laser (DFB-LD) or a distributed Bragg reflection laser (DBR-LD) can be used.

  Similarly to the comparative example, the wavelength controller 112 also controls the wavelength of continuous light output from the semiconductor laser 111 in accordance with a control signal from the corresponding optical receiver 150. In the case of DFB-LD, the wavelength of continuous light is controlled by temperature. For example, when a Peltier element is used, the wavelength can be controlled by a voltage from the wavelength controller 112. In the case of DBR-LD, the wavelength of continuous light is controlled by a bias current, and can be controlled by the current from the wavelength controller 112. In each case of DFB-LD and DBR-LD, if the amount of change in wavelength with respect to unit voltage or unit current is known in advance, wavelength control corresponding to the detected amount of change can be performed. The intensity modulator 113 modulates the intensity of continuous light output from the semiconductor laser 111 according to the transmitted data signal.

  Next, the wavelength multiplexer 120 wavelength-multiplexes the optical signals output from the optical transmitters 110-1 to 110-N to generate a WDM signal. As the wavelength multiplexer, an optical filter such as an arrayed waveguide diffraction grating (AWG) or a fiber grating can be used as in the comparative example. Also, an optical coupler can be used instead of an optical filter. The WDM signal output from the wavelength multiplexer is transmitted to the wavelength demultiplexer 140 via the optical fiber 130. The wavelength demultiplexer 140 demultiplexes the WDM signal according to the wavelength and outputs the demultiplexed signal to each of the optical receivers 50-1 to 50 -N. As the wavelength demultiplexer, for example, an arrayed waveguide diffraction grating (AWG) can be used.

Next, the wavelength stabilization mechanism in the first embodiment of the present invention will be described. The wavelength transmission characteristics of AWG change with temperature. Therefore, for example, when a Peltier element is used, the transmission characteristics of the AWG can be controlled by the voltage from the temperature setting device 161. Therefore, when a sine wave signal having a frequency f is added to the temperature setting signal from the temperature setting device, and the AWG temperature is changed around the set value, the transmission characteristics of the AWG also change according to the temperature change as shown in FIG. Dithering is performed (dithering width = 2A). The time variation of the transmission center wavelength λ of the AWG is modulated by a sine wave having a frequency f centering on the transmission center wavelength λ _c in the setting value of the temperature setting device, and therefore is expressed as the following equation.

At this time, the wavelength change of the optical signal appears as a change in intensity that varies depending on the deviation between the transmission center wavelength λ _c of the AWG and the center wavelength λ ₀ of the optical signal. This intensity change will be described with reference to FIG.

The transmission center wavelength λ of the AWG is modulated as shown in FIG. 8A by the dithered signal from the adder 163. When the set transmission center wavelength λ _c of the AWG matches the center wavelength λ ₀ of the optical signal, an intensity modulation component of frequency 2f appears in the optical signal after AWG transmission as shown in FIG. 8B. This is because the intensity of the optical signal after passing through the AWG becomes maximum when the transmission center wavelength λ of the AWG coincides with the center wavelength (λ ₀ = λ _c ) of the optical signal, and the center wavelength of the optical signal (λ ₀ This is because it becomes the minimum when the displacement is maximized from = λ _c ).

On the other hand, when the center wavelength λ ₀ of the optical signal is shifted from the transmission center wavelength λc of the AWG by a half (A) or more of the dithering width, the optical signal after AWG transmission is shown in FIG. ), An intensity modulation component of frequency f appears. This is because the intensity of the optical signal after passing through the AWG is maximized when the transmission characteristics of the AWG are shifted toward the center wavelength λ ₀ of the optical signal and minimized when shifted in the reverse direction. .

Further, according to the magnitude relationship between the transmission center wavelength λ _c of the AWG and the center wavelength λ ₀ of the optical signal, as shown in FIGS. 8C and 8D, the intensity modulation component of the optical signal after the AWG transmission The phase is reversed. This is because the slope of the transmission characteristics of the AWG is reversed according to the magnitude relationship between λ ₀ and λ _c . When the center wavelength λ ₀ of the optical signal deviates from the transmission center wavelength λ _c of the AWG within a range equal to or less than half the dithering width, the frequency f and 2f are included in the optical signal after AWG transmission. Both intensity modulation components will appear.

The optical signal after AWG transmission includes the intensity modulation component as described above by dithering the transmission characteristics of the AWG, and this optical signal is converted into an electric signal by the photoelectric converter 151 of the optical receiver 150, Processing is performed by the control signal detection unit 152. Specifically, an intensity modulation component of the frequency f is extracted from the electric signal converted by the photoelectric converter 151 through a band pass filter (BPF) 153. The extracted intensity modulation component of frequency f is multiplied by a sine wave signal of frequency f from sine wave signal source 162 by multiplier 154. Here, when the center wavelength λ ₀ of the optical signal is shifted to the longer wavelength side than the transmission center wavelength λ _{c of the} AWG (λ ₀ > λ _c ), the sine wave signal from the sine wave signal source 162 is obtained. Are phase-locked so that they are in phase, the phase is reversed when λ ₀ <λ _c . Further, the maximum amplitude of the intensity modulation component becomes zero when λ ₀ = λ _c and increases as the wavelength difference increases. Therefore, when the DC component of the signal multiplied by the multiplier 154 is extracted by the low-pass filter (LPF) 155, the sign is positive when λ ₀ > λ _c , and the sign is negative when λ ₀ <λ _c. Become. Further, as shown in FIG. 9, the amplitude of the direct current component becomes zero when λ ₀ = λ _c and increases as the wavelength difference increases. This signal is fed back to the wavelength controller 112 of the optical transmitter, and the output wavelength of the semiconductor laser 111 is controlled, so that the center wavelength λ ₀ of the optical signal output from the optical transmitter is changed to the transmission center of the wavelength demultiplexer 140. it can be matched with the wavelength lambda _c.

  As described above, according to the first embodiment of the present invention, the SNR deterioration of the control signal is prevented by dithering the transmission characteristics of the AWG as the wavelength demultiplexer, and the optical transmitter and the optical receiver The circuit configuration can be simplified.

(Second Embodiment)
In the above comparative example, the optical transmitter is limited to a configuration using a semiconductor laser and an intensity modulator. This is because the intensity modulator generated by modulating the wavelength of the optical signal must be canceled by the intensity modulator. However, in the present invention, not only the optical transmitter using the semiconductor laser and the intensity modulator shown in FIG. 6 but also the direct modulation optical transmitter that directly drives the bias current of the semiconductor laser with a data signal is used. You can also.

  FIG. 10 shows a wavelength division multiplexing communication system that stabilizes the wavelength of signal light according to the second embodiment of the present invention. As in the case of the first embodiment, this communication system includes a plurality of optical transmitters 210-1 to 210 -N, a wavelength multiplexer 120, an optical fiber 130, a wavelength demultiplexer 140, and a plurality of optical transmitters. Receivers 150-1 to 150-N. As shown in the figure, the second embodiment of the present invention can have the same configuration as that of the first embodiment except for the configuration of the optical transmitter. Therefore, the same components as those of the first embodiment are denoted by the same reference numerals as those in FIG.

The optical transmitter 210 includes a semiconductor laser 211 and a wavelength controller 212. In the second embodiment of the present invention, a distributed feedback laser (DFB-LD) can be used as the semiconductor laser 211 as a semiconductor laser that can be directly modulated. The output wavelength of the DFB-LD is controlled by temperature. For example, when a Peltier element is used, the wavelength can be controlled by the voltage from the wavelength controller 212. Therefore, as in the case of the first embodiment described above, the output wavelength of the semiconductor laser 211 is controlled based on the wavelength control signal from the corresponding optical receiver 150 to be output from the optical transmitter 210. The center wavelength λ ₀ of the optical signal can be matched with the transmission center wavelength λ _{c of the} wavelength demultiplexer 140.

  As described above, according to the second embodiment of the present invention, since the intensity modulator is not required, the configuration of the optical transmitter can be simplified. In the above comparative example, in order to cancel the intensity modulation component generated by modulating the wavelength of the optical signal, the use of the intensity modulator is indispensable, and the direct drive type optical transmission as in this embodiment is performed. Cannot be used.

(Third embodiment)
The third embodiment of the present invention relates to optimizing a fluctuation range due to dithering of transmission characteristics of an AWG. Specifically, the fluctuation range due to dithering of the transmission characteristics of the AWG is optimized in accordance with the spread of the spectrum of the optical signal.

  FIG. 11 shows the transmission of an AWG that can multiplex / demultiplex an optical spectrum when a dominant DFB-LD of an adiabatic chirp is directly modulated with a 1.25 GHz (PN7 stage) data signal and a WDM signal at 50 GHz intervals. An example of characteristic measurement is shown. As can be seen in the figure, the transmission characteristics of the AWG are symmetric with respect to the transmission center wavelength (relative frequency 0 GHz in the figure), whereas the spectrum of the directly modulated optical signal is symmetric with respect to the left and right. . In addition, the optical spectrum spreads beyond ignorance with respect to the transmission width of AWG (3 dB width = 27.5 GHz). Here, the relative frequency of the light spectrum of direct modulation indicates that the light intensity reaches a peak at 0 GHz. Although the spread of the optical spectrum by direct modulation is being improved by recent research and development, the spread cannot be ignored when considering application to high-density WDM such as 50 GHz intervals and 100 GHz intervals.

FIG. 12 shows measurement results showing the influence of optical spectrum spread and asymmetry due to direct modulation. The DFB-LD and AWG used are the same as those shown in FIG. The horizontal axis of the figure represents the transmission center wavelength shift (frequency shift) of the AWG, and the vertical axis represents the relative light intensity and the power penalty, respectively. The relative light intensity represents the degree to which the intensity of the optical signal that has passed through the AWG changes when the transmission center wavelength of the AWG is shifted relative to the wavelength of the DFB-LD, and is normalized to a maximum value of 0 dB. Yes. The power penalty represents a deterioration in reception sensitivity when an optical signal transmitted through the AWG is received using an APD having a reception sensitivity of −34.2 dBm at BER = 10 ⁻¹² .

  In this case, if the spread of the optical spectrum by direct modulation is negligibly small with respect to the transmission width of the AWG, a region where the relative light intensity and the power penalty are 0 dB should be obtained. However, as seen in the figure, there are few such regions, and the relative light intensity and power penalty are each sensitively sensitive to AWG frequency shifts. Moreover, since the optical spectrum is asymmetrical, any curve is asymmetric with respect to the AWG frequency shift.

  FIG. 13 shows how much the loss budget allowed for the optical fiber transmission line 130 decreases due to the decrease in relative light intensity and the degradation of power penalty that occur in this wavelength stabilizing device. This loss budget reduction is defined as the loss budget penalty. Both the reduction in relative light intensity and the degradation of power penalty lead to a reduction in loss budget allowed in the transmission line. Therefore, the difference between the power penalty and the relative light intensity is shown as the loss budget penalty on the vertical axis of FIG. As seen in the figure, the penalty of the loss budget changes asymmetrically with respect to the AWG frequency shift of 0 GHz. For example, when designing a wavelength stabilizing device that allows a loss budget penalty of 3 dB, the frequency deviation allowed by the AWG is -4.5 GHz to 8 GHz. In this case, if the intensity peak in the optical spectrum of the signal light is controlled to coincide with the transmission center wavelength of the AWG, the loss budget penalty due to the AWG frequency shift becomes stricter on the low frequency side, and the optimum wavelength stability It will not be made. In the case shown in FIG. 13, the frequency shift of the AWG that minimizes the penalty for the loss budget is +1.75 GHz, and the characteristics are almost symmetrical at this position. According to FIG. 12, the relative light intensity becomes zero when the frequency shift of the AWG is approximately 0 GHz, and the wavelength of the semiconductor laser is normally locked at this position. Therefore, optimal wavelength stabilization can be achieved by controlling the wavelength of the semiconductor laser to a value offset by -1.75 GHz from the transmission center wavelength of the AWG in the wavelength controller.

  Note that when using a direct modulation type optical transmitter as in the second and third embodiments, the influence of the spread of the optical spectrum is large, so the wavelength multiplexer is not an optical filter such as an AWG, It is desirable to use an optical coupler.

(Fourth embodiment)
In the third embodiment of the present invention, the magnitude of the wavelength control signal changes in proportion to the magnitude of the optical power received by the optical receiver. That is, the magnitude of the wavelength control signal changes according to the distance between the optical transmitter and the optical receiver. For this reason, the offset value set to minimize the loss budget penalty must also be changed in proportion to the optical power. The fourth embodiment of the present invention relates to changing the offset value of the wavelength control signal according to the received optical power.

  FIG. 14 shows a configuration of an optical receiver according to the fourth embodiment of the present invention. As shown in the figure, the optical receiver 250-1 further includes an optical power detector 251 for detecting the received optical power, an α-multiplier 252, in addition to the configuration of the optical receiver 150-1 in FIG. And an adder 253 for adding an offset value to the wavelength control signal. The optical power detector 251 outputs a signal proportional to the magnitude of the signal from the photoelectric converter 151. The multiplier 252 multiplies the output of the optical power detector by α and outputs an offset value corresponding to the optical power. This offset value is added to the wavelength control signal by the adder 253 and fed back to the optical transmitter 110-1.

  With this configuration, an appropriate offset amount can be added to the wavelength control signal according to the magnitude of the optical power received by the optical receiver, and the distance between the optical transmitter and the optical receiver can be changed. In addition, an appropriately offset wavelength control signal can be fed back. Here, α can be set as a fixed value for each apparatus.

(Fifth embodiment)
FIG. 15 shows a wavelength division multiplexing communication system that stabilizes the wavelength of signal light according to the fifth embodiment of the present invention. As in the case of the second embodiment, this communication system includes a plurality of optical transmitters 210-1 to 210-N, a wavelength multiplexer 120, an optical fiber 130, a wavelength demultiplexer 140, and a plurality of optical transmitters. Receivers 350-1 to 350-N. As shown in the figure, the fifth embodiment of the present invention can have the same configuration as the second embodiment except for the configuration of the control signal detector. Therefore, the same components as those in the second embodiment are denoted by the same reference numerals as those in FIG. 10 and description thereof is omitted.

In the fifth embodiment of the present invention, the optical receivers 350-1 to 350-N have a configuration in which the control signal detection unit 352 is shared. By switching the electrical signal from the photoelectric converter 351 of each optical receiver via the switch 356, a wavelength control signal can be generated for each optical receiver. Specifically, as in the case of the above embodiment, the intensity modulation component of the frequency f is extracted from the electric signal converted by the photoelectric converter 151 via the band pass filter (BPF) 353. The extracted intensity modulation component of frequency f is multiplied by a sine wave signal of frequency f from sine wave signal source 162 in multiplier 354. Then, the signal multiplied by the multiplier 354 is extracted by a low-pass filter (LPF) 355 to obtain a wavelength control signal. This signal is fed back to the wavelength controller 212 of the optical transmitter, and the output wavelength of the semiconductor laser 211 is controlled, whereby the center wavelength λ ₀ of the optical signal output from the optical transmitter is changed to the transmission center of the wavelength demultiplexer 140. it can be matched with the wavelength lambda _c. The switch 356 may be switched at a predetermined time interval or may be switched according to a request or operation of the optical transmitter or optical receiver.

  According to the fifth embodiment of the present invention, the configuration of the optical receiver can be simplified by sharing the control signal detection unit 352.

(Sixth embodiment)
Since the above-described method of changing the transmission center wavelength of a wavelength demultiplexer (for example, AWG) is based on a temperature change of the wavelength demultiplexer, the upper limit of the dithering frequency f is about 1 kHz. Accordingly, the intensity-modulated signal having the frequency f superimposed on the electrical signal converted by the photoelectric converter 151 appears in the vicinity of zero hertz assuming an NRZ signal of the order of Gbps. This is shown in FIG. Here, B in the figure represents the bit rate of the data signal.

  In this case, if the intensity modulated signal having the frequency f is extracted by the electrical BPF 153, the signal component becomes noise, and the SNR of the detected wavelength control signal deteriorates. This problem can be reduced by using a signal having a drop in the low frequency component of the electrical spectrum, as shown in FIG. Examples of such a signal include a Gigabit Ethernet (registered trademark) (GbE: Gigabit Ethernet (registered trademark)) signal defined in IEEE Std 802.3z-1998 and a Manchester signal.

  FIG. 17 shows the measurement result of the electrical spectrum when a PN9 stage pseudo-random signal is inserted into the data frame of the GbE signal. As shown in the figure, there is a drop in the signal component at a frequency of 60 MHz or less. This drop of the signal component is caused by performing 8B → 10B conversion when converting an electrical signal into an optical signal. Therefore, when a dithering frequency of 1 kHz or less is used, the SNR of the wavelength control signal can be greatly improved as compared with the NRZ signal having the electrical spectrum shown in FIG.

  FIG. 18A represents the electrical spectrum of the Manchester signal. As shown in the figure, the signal spectrum of the data is different from that of FIG. 16B and has spread to twice the signal bit rate (= 2B), but there is a drop in the low frequency component.

  FIG. 18B shows a time waveform of the Manchester signal. As shown in the figure, this signal is generated by representing one bit of mark (M) and space (S) by a combination of plus and minus amplitudes and a combination of minus and plus amplitudes, respectively. Here, the relationship between these combinations and bits may be reversed.

  Note that there may be a case where an optical signal cannot be generated by an electric signal having a negative amplitude, as in the direct modulation DFB-LD. In that case, as shown in FIG. 18C, an optical signal can be generated by biasing the signal of FIG. 18B.

  Thus, according to this embodiment, the SNR of the wavelength control signal can be improved by using a specific signal.

(Seventh embodiment)
FIG. 19 shows an example using two MZI circuits and AWGs as wavelength transmission means and dithering means according to the seventh embodiment of the present invention. FIG. 19 shows a part of the wavelength multiplexing communication system shown in FIG.

  The wavelength multiplexer / demultiplexer 440 is connected to a Mach-Zehnder interferometer (MZI) circuit 441 that separates wavelength-multiplexed signal light into odd-numbered wavelength channels and even-numbered wavelength channels, and one output port 445 of the MZI circuit. The arrayed waveguide diffraction grating (AWG) 443 and the arrayed waveguide diffraction grating (AWG) 444 connected to the other output port 446 of the MZI circuit. The MZI circuit and the two AWGs can be manufactured using an optical waveguide on a flat substrate. When an optical waveguide is used, there is an advantage that wavelength transmission characteristics can be set with high accuracy, the MZI circuit and the AWG are integrated and downsized, and can be produced at low cost.

  The free spectral range (FSR) of the MZI circuit 441 and the wavelength channel interval of the AWGs 443 and 444 are set to twice the interval of the signal light wavelength. One output 445 of the MZI circuit is connected to an AWG 443 that outputs odd-numbered wavelength signal light and demultiplexes the wavelength signal light. The other output 446 of the MZI circuit is connected to an AWG 444 that outputs even-numbered wavelength signal light and demultiplexes the wavelength signal light. A wavelength demultiplexer 440 is configured by the MZI circuit and the two AWGs as a whole.

  The output voltage of the sine wave signal source 162 and the DC voltage output from the center wavelength setting unit 461 are added by the adder 163 and added to the phase modulator 442 provided in the MZI circuit 441. The phase modulator 442 can shift the entire periodic transmission center wavelength of the MZI circuit by changing the optical path length of one optical path of the MZI circuit. As the phase modulator, a thin film heater that uses the thermo-optic effect of an optical waveguide is generally used, but the same effect can be obtained by using an effect that makes other optical paths variable such as an electro-optic effect.

  The output of the center wavelength setting unit 461 is set so that the transmission center wavelength of the MZI circuit matches the target wavelength of each channel of the wavelength-multiplexed signal light or gives an offset within a range in which the transmitted light intensity does not greatly decrease. . The operation of the wavelength demultiplexer when a sine wave signal is applied in this state is shown in FIG.

  Wavelengths λc1 to λc6 are stabilization target wavelengths of the wavelength-division multiplexed signal lights. The transmission center wavelengths of the output 1 (445) and AWG1 (443) of the MZI circuit are odd-numbered signal wavelengths, and the transmission center wavelengths of the output 2 (446) and AWG2 (444) of the MZI circuit are even-numbered signal wavelengths. It is adapted to. Since the transmittance of the wavelength demultiplexer 440 is determined by the product of the transmittances of the MZI circuit 441 and the AWGs 443 and 444, all dithering signals are input to the phase modulator 442 in the MZI circuit. The transmission characteristics of the output port are dithered. Further, as shown in FIG. 20, since the FSR of the MZI circuit, that is, the transmission wavelength period is twice the channel interval of the wavelength division multiplexed signal, the transmission band of each channel of the wavelength demultiplexer becomes wider, and the signal light It can be seen that it also functions sufficiently as a demultiplexing means.

  Since the thin film heater in the MZI circuit has a small heat capacity in the heated portion, it can perform dithering at high speed with low power. In the MZI circuit manufactured by the quartz optical waveguide circuit, a center wavelength change of 2 GHz amplitude was obtained with a heater power amplitude of 8 mW. Moreover, it was confirmed that the wavelength change can follow up to a dithering frequency of 100 Hz or more.

  As described above, according to the present embodiment, it is possible to configure a wavelength demultiplexer capable of high-speed dithering with low power consumption.

(Eighth embodiment)
FIG. 21 shows an example using a thin film heater provided on the AWG as the dithering means according to the eighth embodiment of the present invention. FIG. 21 shows a part of the wavelength multiplexing communication system shown in FIG.

  The wavelength demultiplexer 540 includes an arrayed waveguide diffraction grating (AWG) 541 that demultiplexes wavelength-multiplexed signal light for each wavelength, and the AWG 541 includes a thin film heater 543 on the surface thereof. The wavelength demultiplexer 540 can be manufactured using an optical waveguide on a flat substrate. The thin film heater 543 is a conductive thin film such as a metal formed on the surface of the arrayed waveguide 543 in the AWG circuit and a power supply lead wire. For the formation of the conductive thin film, a general film forming process such as vapor deposition, sputtering, and metal foil pasting can be used.

  The output power of the sine wave signal source 162 and the DC voltage output from the center wavelength setting unit 461 are added by the adder 163 and applied to the thin film heater 543, thereby modulating the temperature of the arrayed waveguide 542 with the frequency f. be able to. The transmission center wavelength of the AWG 541 is dithered due to the thermo-optic effect of the waveguide material.

  The thin film heater 543 and the arrayed waveguide 542 heated by the thin film heater have a small heat capacity because their thickness is as thin as several μm to several tens of μm. Therefore, less power is required for dithering and the response frequency is higher. In the combination of the AWG using the quartz glass material and the thin film heater using the gold alloy thin film, a center wavelength change of 2 GHz amplitude was obtained with a heater power amplitude of 400 mW. It was also confirmed that the wavelength change can follow up to a dithering frequency of 10 Hz or more.

  In this embodiment, it is only necessary to add a thin film heater to the AWG of the wavelength demultiplexer, and a wavelength demultiplexer capable of high-speed dithering at low cost can be configured.

  While the present invention has been described with respect to several specific embodiments, the embodiments described herein are merely illustrative in view of the many possible embodiments to which the principles of the present invention can be applied. It is not intended to limit the scope of the invention. For example, the fifth embodiment shows an example applied to the second embodiment, but the fifth embodiment can also be applied to the first embodiment. Therefore, the configuration and details of the embodiment exemplified herein can be changed as necessary without departing from the spirit of the present invention. Further, the illustrative components and procedures may be changed, supplemented, or changed in order without departing from the spirit of the invention.

It is a functional block diagram which shows an example of the wavelength multiplexing communication system which stabilizes the wavelength of signal light, without using a wavelength locker. It is a figure for demonstrating the mechanism by which the wavelength change of an optical signal is converted into an intensity | strength change by a wavelength transmission characteristic, FIG. 2 (a) shows a wavelength transmission characteristic, FIG.2 (b) shows the 1st-order differential characteristic. Show. It is a figure which shows the signal waveform of each part in the optical transmitter of FIG. It is a figure which shows the wavelength change of each part in the optical transmitter of FIG. It is a figure which shows the spectrum of each signal converted into the electrical signal in the optical receiver of FIG. It is a functional block diagram which shows an example of the wavelength multiplexing communication system which stabilizes the wavelength of signal light according to the 1st Embodiment of this invention. It is a figure which shows the relationship between the dithering of the wavelength transmission characteristic in the 1st Embodiment of this invention, and the center wavelength of an optical signal. It is a figure for demonstrating the intensity | strength modulation component of the optical signal by the dithering of the wavelength transmission characteristic in the 1st Embodiment of this invention. It is a figure which shows the wavelength transmission characteristic of AWG in the 1st Embodiment of this invention, and the amplitude characteristic of a wavelength control signal. It is a functional block diagram which shows an example of the wavelength division multiplexing communication system which stabilizes the wavelength of signal light according to the 2nd Embodiment of this invention. It is a figure which shows the optical transmission spectrum at the time of directly modulating the wavelength transmission characteristic of AWG and a semiconductor laser. It is a figure which shows the relationship between the frequency shift from the transmission center wavelength of AWG of an optical signal, relative light intensity, and a power penalty. It is a figure which shows the relationship between the frequency shift from the transmission center wavelength of AWG of an optical signal, and the penalty of a loss budget. It is a functional block diagram which shows an example of the optical receiver which produces | generates a wavelength control signal according to the 4th Embodiment of this invention. It is a functional block diagram which shows an example of the wavelength multiplexing communication system which stabilizes the wavelength of a signal beam | light according to the 5th Embodiment of this invention. It is a figure which shows the effect of the spectrum in the 6th Embodiment of this invention. It is a figure which shows the measurement result of an electrical spectrum when inserting the pseudorandom signal of PN9 stage into the data frame of GbE signal. FIG. 18A is a diagram showing a Manchester signal, FIG. 18A is an electrical spectrum, FIG. 18B is a time waveform, and FIG. 18C is a time waveform when biased. It is a functional block diagram which shows a part of wavelength multiplexing communication system which stabilizes the wavelength of a signal beam | light according to the 7th Embodiment of this invention. It is a figure which shows the wavelength transmission characteristic of each part of the wavelength demultiplexer in the 7th Embodiment of this invention. It is a functional block diagram which shows a part of wavelength multiplexing communication system which stabilizes the wavelength of a signal beam | light according to the 8th Embodiment of this invention.

Explanation of symbols

10-1 to N optical transmitter 11 semiconductor laser 12 wavelength controller 13 intensity modulator 14 sine wave signal source 15 current source 16 polarity inverter 17 frequency divider 18 adder 20 wavelength multiplexer 30 optical fiber 40 wavelength demultiplexing 50-1 to N Optical receiver 51 Photoelectric converter 52 Control signal detector 53 BPF1
54 Multiplier 55 LPF
56 BPF2
57 Multiplier 110-1 to N Optical Transmitter 111 Semiconductor Laser 112 Wavelength Controller 113 Intensity Modulator 120 Wavelength Multiplexer 130 Optical Fiber 140 Wavelength Demultiplexer 150-1 to N Optical Receiver 151 Photoelectric Converter 152 Control Signal detector 153 BPF
154 Multiplier 155 LPF
161 Temperature setting unit 162 Sine wave signal source 163 Adder 210-1 to N Optical transmitter 211 Semiconductor laser 212 Wavelength controller 250-1 Optical receiver 251 Optical power detector 252 Multiplier 253 Adder 350-1 to N light Receiver 351 Photoelectric converter 352 Control signal detector 353 BPF
354 Multiplier 355 LPF
356 Switcher 440 Wavelength demultiplexer 441 MZI circuit 442 Phase modulator 443,444 AWG
445, 446 Output port 461 Center wavelength setting unit 540 Wavelength demultiplexer 541 AWG
542 Arrayed Waveguide 543 Thin Film Heater

Claims (8)

Wavelength transmission means for transmitting an optical signal from the transmission side on the reception side with a predetermined wavelength transmission characteristic;
Dithering means for dithering the wavelength transmission characteristic on the receiving side at a predetermined frequency;
Photoelectric conversion means for converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal;
Filter means for extracting a signal of the predetermined frequency from the electrical signal converted by the photoelectric conversion means;
A signal generation means for generating a wavelength control signal for controlling the wavelength of the optical signal on the transmission side from the phase component and the amplitude component of the extracted signal, and feeding back to the transmission side;
The signal generating means offsets the wavelength control signal that is offset from the transmission center wavelength of the wavelength transmitting means by a wavelength shift that minimizes the amount of loss budget loss allowed in the optical fiber transmission path through which the optical signal has propagated. A wavelength stabilizing device generated and fed back to the transmitting side . The wavelength stabilization device according to claim 1,
The wavelength transmission means is an arrayed waveguide diffraction grating that transmits an optical signal in which a plurality of wavelengths are multiplexed with a predetermined wavelength transmission characteristic according to the wavelength,
The dithering means dithers the wavelength transmission characteristics of the arrayed waveguide grating at a predetermined frequency,
The photoelectric conversion means converts optical signals of a plurality of wavelengths that have transmitted the dithered wavelength transmission characteristics into a plurality of electrical signals, respectively.
The wavelength stabilizing device, wherein the filter unit and the signal generation unit are configured to share the plurality of electric signals via a switch. In the wavelength stabilization apparatus in any one of Claim 1 and 2,
The wavelength transmitting means is connected to a Mach-Zehnder interferometer circuit having a first output and a second output, a first arrayed waveguide grating connected to the first output, and the second output. The Mach-Zehnder interferometer circuit divides an optical signal in which a plurality of wavelengths are multiplexed into an odd-numbered wavelength group and an even-numbered wavelength group according to the wavelength. The optical signal of the odd-numbered wavelength group is output via the first output, the optical signal of the even-numbered wavelength group is output via the second output, and the first wavelength transmission The first arrayed waveguide diffraction grating transmits the transmitted optical signal of the odd-numbered wavelength group with a second wavelength transmission characteristic, and the second arrayed waveguide diffraction grating is Before that permeated The optical signal of the even-numbered wavelength group is transmitted at the third wavelength transmission characteristics,
The wavelength stabilizing device, wherein the dithering means is configured to dither the first wavelength transmission characteristic of the Mach-Zehnder interferometer circuit at a predetermined frequency. In the wavelength stabilization apparatus in any one of Claim 1 thru | or 3 ,
The wavelength stabilizing device, wherein the signal generating unit generates a signal for controlling the wavelength of the optical signal so that the wavelength of the optical signal matches the center wavelength of the predetermined wavelength transmission characteristic. Transmitting an optical signal from the transmitting side with a predetermined wavelength transmission characteristic on the receiving side;
Dithering the receiving side wavelength transmission characteristics at a predetermined frequency;
Converting an optical signal transmitted through the dithered wavelength transmission characteristic into an electrical signal;
Extracting the signal of the predetermined frequency from the converted electrical signal;
Generating a wavelength control signal for controlling the wavelength of the optical signal on the transmission side from the phase component and amplitude component of the extracted signal, and feeding back to the transmission side,
The generating step offsets the wavelength control signal that is offset from the transmission center wavelength of the wavelength transmission means by a wavelength shift that minimizes the amount of loss budget loss allowed in the optical fiber transmission path through which the optical signal has propagated. A wavelength stabilization method comprising generating and feeding back to the transmission side . In the wavelength stabilization method according to claim 5,
The transmitting step transmits an optical signal in which a plurality of wavelengths are multiplexed with a predetermined wavelength transmission characteristic according to the wavelength,
The dithering step dithers the wavelength transmission characteristic at a predetermined frequency;
The converting step converts optical signals of a plurality of wavelengths that have passed through the dithered wavelength transmission characteristics into a plurality of electrical signals, respectively.
A wavelength stabilization method, wherein the plurality of electrical signals are switched to perform the extracting step and the generating step. In the wavelength stabilization method in any one of Claim 5 and 6,
The transmitting step divides an optical signal in which a plurality of wavelengths are multiplexed into an odd-numbered wavelength group and an even-numbered wavelength group according to the wavelength, and the optical signal of each wavelength group has a first wavelength transmission characteristic. Transmitting the optical signal of the transmitted odd-numbered wavelength group for each wavelength and transmitting the optical signal with the second wavelength transmission characteristics, and transmitting the transmitted even-numbered wavelength group of the even-numbered wavelength group. Further demultiplexing the optical signal for each wavelength and transmitting each of the signals with a third wavelength transmission characteristic,
The dithering step comprises dithering the first wavelength transmission characteristic. In the wavelength stabilization method in any one of Claim 5 thru | or 7 ,
The generating step generates a signal for controlling the wavelength of the optical signal so that the wavelength of the optical signal matches the center wavelength of the wavelength transmission characteristic.

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