JP2012231186A - Wavelength variable optical transmitter and optical transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength variable optical transmitter which is compact and has a high yield and is low-cost by using a semiconductor optical element in which an electrical field absorption modulator and a semiconductor laser are integrated on the same substrate, and at the same time can keep modulation/transmission characteristics constant.SOLUTION: A wavelength variable laser module for DWDM which mounts one electrical field absorption modulator integrated laser, and can be varied in oscillation wavelength by temperature control is used. Driving conditions of the laser and the modulator are determined so that modulation/transmission characteristics can be kept nearly constant in a temperature control range. By using such the electrical field absorption modulator integrated laser and being built in the driving conditions, a wavelength variable optical transmitter which is compact and low-cost can be provided.

Description

  The present invention relates to a tunable optical transmitter and an optical transceiver, and more particularly to a tunable optical transmitter and an optical transceiver that operate stably over a wide range of wavelength channels.

  At present, wavelength division multiplexing (DWDM) optical transmission that transmits multiple wavelengths of optical signals over a single optical fiber, which is widely used in trunk systems, realizes long-distance and large-capacity optical transmission. This is an important transmission method. For DWDM optical transmission, the grid wavelength (wavelength channel) is defined in the 1.55 μm wavelength band that realizes long-distance optical transmission in the ITU-T standard, and the wavelength interval (frequency interval) is 0.4 nm (50 GHz). Or 0.8 nm (100 GHz).

  In recent years, development of a tunable optical transmitter that can cover the wavelengths of a plurality of channels with one optical transmitter has been underway. This wavelength tunable optical transmitter only needs to change the oscillation wavelength at the wavelength interval for DWDM, and other characteristics (optical output power, modulation characteristics, transmission characteristics, etc.) need to remain constant regardless of the wavelength. is there.

  Currently, there are roughly two types of laser modules used in wavelength tunable optical transmitters for DWDM. One is a method using a plurality of laser arrays, and the other is a method of changing the temperature of one laser.

The former includes a plurality of distributed feedback lasers (DFB-LDs) in which the pitch of the diffraction grating is changed so as to oscillate at different oscillation wavelengths at wavelength intervals for DWDM.
Diode (LD) or distributed Bragg reflector laser diode (DBR-LD) is an LD array integrated on one semiconductor optical device. In this configuration, a multi-mode interference (MMI) multiplexer and a semiconductor optical amplifier (SOA) are generally integrated in the same element. The MMI multiplexer combines the oscillation light from each LD array into one waveguide, and the SOA is for compensating for the loss of optical power in the MMI. When an LD array is used, the oscillation wavelength can be varied by the number of LD arrays even when the temperature of the semiconductor optical element is kept constant, so that many channels can be covered.

  In order to modulate oscillation light having a plurality of wavelengths from the LD array, an external modulator such as an EA modulator may be integrated in front of the SOA. However, an integrated external modulator can only operate in a wavelength range where the modulation characteristics and transmission characteristics can be kept constant. For this reason, generally, a lithium niobate (LN: LiNbO3) modulator module having a small wavelength dependency with respect to modulation / transmission characteristics is often provided outside the wavelength tunable laser module.

  In Patent Document 1, a semiconductor laser device having a configuration in which an LD array, a coupler (multiplexer), one semiconductor optical amplifier, and one EA modulator are combined, and the offset bias of the EA modulator is changed. Driving is described. As a corresponding US patent of Patent Document 1, there is US Pat. No. 6,516,017.

  The latter is one DFB-LD (EA / DFB: electroabsorption modulator integrated DFB laser) in which one EA modulator is integrated. In this case, the oscillation wavelength is changed by changing the temperature of the EA / DFB element to match the wavelength channel for DWDM.

  Patent Document 2 describes an optical transmitter that separately controls the temperature of a semiconductor laser and an electroabsorption modulator. This optical module can change the wavelength by changing the temperature of the semiconductor laser and feed back the information of the wavelength to the temperature control of the modulator, thereby obtaining a constant characteristic without changing the drive bias of the modulator. it can.

  Non-Patent Document 1 describes an indium gallium aluminum arsenide (InGaAlAs) EA / DFB laser that can be used without cooling in the range of 0 ° C. to 85 ° C. Non-Patent Document 1 also describes that the oscillation wavelength of 1550 nm at 0 ° C. is about 1560 nm at 85 ° C.

JP 2001-144367 A JP 2005-045548 A

S. Makino et al., "Wide Temperature Range (0 to 85 ℃), 40-km SMF Transmission of a 1.55-μm, 10Gbit / s InGaAlAs Electroabsorption Modulator Integrated DFB Laser", OFC2005, PDP14

  In the semiconductor laser device of Patent Document 1, it is difficult to reduce the overall module size. In addition, since there are many types of functional elements integrated on one element, there is a concern that the yield in manufacturing the element will be very poor.

  In the optical transmitter of Patent Document 2, the semiconductor laser and the electroabsorption modulator are separate elements, and a coupling loss between the two inevitably occurs. In addition, since the temperature of the semiconductor laser and the electroabsorption modulator are separately controlled, it is difficult to reduce the size and power consumption.

  The present invention uses one EA modulator / laser. In this case, it is used in a wide temperature range, and it is necessary to adjust the driving conditions of the laser element and the EA modulator element. According to the present invention, there is provided a small-sized, high-yield, low-cost tunable optical transmitter that does not change its characteristics as an EA modulator integrated laser even when the driving conditions are changed.

  The above-described problems include an electroabsorption modulator integrated laser in which an electroabsorption modulator and a semiconductor laser are integrated on a substrate, a temperature control unit that adjusts the temperature of the electroabsorption modulator integrated laser, and a semiconductor laser. The temperature controller comprises a laser driver for driving and a modulator driver for driving the electroabsorption modulator, and the temperature controller changes the temperature of the electroabsorption modulator integrated laser to change the oscillation wavelength of the semiconductor laser to 3 nm. The laser drive unit and the modulator drive unit are variable in the above wavelength range, and the semiconductor laser and the electroabsorption type modulation are used so that the electroabsorption modulator integrated laser has almost the same modulation characteristics and transmission characteristics in the wavelength range. This can be achieved by a tunable optical transmitter that drives the transmitter.

  Further, an electroabsorption modulator integrated laser in which an electroabsorption modulator and a semiconductor laser are integrated on a substrate, a temperature control unit for adjusting the temperature of the electroabsorption modulator integrated laser, and a laser for driving the semiconductor laser The laser drive unit includes a drive unit and a modulator drive unit that drives the electroabsorption modulator, and the laser drive unit converts the current applied to the semiconductor laser to a temperature within a temperature range of 30 ° C. or more given by the temperature control unit. The modulator driver changes the amplitude voltage of the high frequency signal applied to the electroabsorption modulator and the reverse voltage applied to the electroabsorption modulator in a temperature range depending on the temperature. This can be achieved by a tunable optical transmitter.

  According to the present invention, it is possible to obtain a wavelength tunable optical transmitter that has a small element size and does not change the output characteristics regardless of the wavelength.

It is a block diagram of the optical transmitter which mounts an EA / DFB element in a wavelength variable module. It is a figure explaining the temperature dependence of the oscillation wavelength of DFB-LD, and the absorption edge wavelength of an EA modulator. It is a figure explaining the element temperature dependence of the electric current-light output (IL) characteristic of a DFB-LD part. It is a figure explaining the element temperature dependence of a static extinction ratio (DCER) characteristic. It is a figure explaining the element temperature dependence of the small signal alpha parameter. It is a figure explaining changing the reverse voltage applied to an EA modulator, and correcting so that the detuning amount (DELTA) H may become constant in each temperature pseudo. It is a figure explaining the result of having calculated | required the drive current Iop of DFB-LD so that the substantially same modulation characteristic and transmission characteristic may be satisfy | filled at each temperature, respectively. It is a figure explaining the result of having calculated | required the reverse voltage Vb applied to an EA modulator so that substantially equivalent modulation and transmission characteristics may be satisfy | filled at each temperature, respectively. It is a figure explaining the result of having calculated | required the voltage amplitude Vpp of the high frequency signal so that substantially the same modulation and transmission characteristics may be satisfied at each temperature. It is a figure explaining the oscillation wavelength in each temperature, a drive condition, a modulation characteristic, and a transmission characteristic. It is a figure explaining the band structure of InGaAsP type MQW and InGaAlAs type MQW. It is a figure explaining the result of having calculated | required the drive current Iop of DFB-LD so that substantially the same modulation and transmission characteristic may be satisfy | filled at each temperature. It is a figure explaining the result of having calculated | required the reverse voltage Vb applied to an EA modulator so that substantially equal modulation and transmission characteristics may be satisfy | filled at each temperature, respectively. It is a figure explaining the result of having calculated | required the voltage amplitude Vpp of the high frequency signal so that substantially the same modulation characteristic and transmission characteristic may be satisfy | filled at each temperature. It is a figure explaining the oscillation wavelength in each temperature, a drive condition, a modulation characteristic, and a transmission characteristic. It is a block diagram of an optical transceiver.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings using examples.

  FIG. 1 is a block diagram of an optical transmitter in which an EA / DFB element is mounted on a wavelength variable module. Here, the EA / DFB element 101 is an element in which a DFB-LD part and an EA modulator part are integrated. The EA / DFB element 101 is mounted on a Peltier substrate 103 for temperature control via a chip carrier 102. A thermistor 104 is mounted on the chip carrier 102 as close to the EA / DFB element 101 as possible, and the temperature of the element is monitored via the chip carrier 102. A part of the forward output light of the EA / DFB element 101 is split by the beam splitter 107 into a monitoring photodiode (monitor PD) 117. The forward output light that has passed through the beam splitter 107 is coupled to the optical fiber 200 by the lens system 108. On the other hand, the rear output light of the EA / DFB element 101 is input to the wavelength locker module 106. Here, the wavelength locker module 106 is an optical component composed of an etalon and two photodiodes, and locks the wavelength by keeping the photocurrent ratio of the two photodiodes before and after passing through the etalon constant. This component realizes high wavelength stability. Conversely, the oscillation wavelength can be monitored from the photocurrent ratio of the two photodiodes.

  The optical transmitter 100 shown in FIG. 1 includes a Peltier temperature control circuit 114, an EA modulator drive driver 111, a laser drive current driver 112, and a drive control circuit 110 in addition to the optical components constituting the wavelength tunable laser module 109 described above. Composed. The Peltier temperature control circuit 114 controls the Peltier substrate 103 so that the resistance value of the normal thermistor 104 is constant. However, when the photocurrent ratio of the two photodiodes of the wavelength locker module 106 deviates from the set value, priority is given to controlling the photocurrent ratio to be constant. This compensates for aging of the DFB-LD. The Peltier temperature control circuit 114 can change the value of the photocurrent ratio to be controlled by a control line (not shown). This is used to change the oscillation wavelength of the DFB-LD.

  The drive control circuit 110 includes an EA modulator control circuit 115 and a laser drive current control circuit 116. The EA modulator control circuit 115 sets the drive condition of the EA modulator in the EA modulator drive driver 111 based on the element temperature obtained from the Peltier temperature control circuit 114. On the other hand, the laser drive current control circuit 116 determines the drive condition of the DFB-LD based on the element temperature obtained from the Peltier temperature control circuit 114 and the intensity of the forward output light detected by the monitoring photodiode 117. Set to.

  The EA modulator driver 111 includes a high frequency amplitude controller 105 and an inverse method voltage controller 113. The EA modulator driver 111 adjusts the high frequency signal with the high frequency amplitude and the inverse method voltage set by the EA modulator control circuit 115 and inputs the adjusted high frequency signal to the EA modulator section of the EA / DFB element 101.

  The laser drive current driver 112 inputs the drive current set by the laser drive current control circuit 116 to the DFB-LD unit of the EA / DFB element 101.

  In order to keep the forward light output constant, APC (Auto Power Control) control is performed in which a minute fluctuation ΔP of the power received by the monitor PD is fed back to the laser drive current source. On the other hand, the temperature control unit 114 of the Peltier substrate 103 determines and keeps the element temperature constant while monitoring the resistance value of the thermistor 104. When the element temperature fluctuates slightly, the oscillation wavelength monitored by the wavelength monitor mechanism fluctuates slightly, so ATC (Auto Temperature Control) control that detects this and returns to the Peltier temperature control unit of the Peltier substrate 103 I do.

  In general, the oscillation wavelength λ of the DFB-LD has a dependency of about 0.1 nm / ° C. because the effective refractive index of the LD portion changes with the element temperature change. By utilizing this fact and intentionally changing the element temperature, the wavelength can be made variable to match the wavelength channel for DWDM. For example, when the element temperature is changed by 90 ° C. from T1 = −5 ° C. to T4 = 85 ° C., the wavelength is changed by about 9 nm (corresponding to 22 channels at 0.4 nm intervals and 11 channels at 0.8 nm intervals). Is possible. On the other hand, when the element temperature, that is, the oscillation wavelength is changed, the information of the Peltier temperature control unit 114 is sent to the control circuit unit 110 that determines the driving condition of the element. By changing the driving conditions of the LD and the modulator in accordance with the element temperature, substantially the same modulation characteristics and transmission characteristics can be obtained over many wavelength channels. Hereinafter, a method for driving the wavelength tunable optical transmitter will be described.

  FIG. 2 is a diagram for explaining the temperature dependence of the oscillation wavelength of the DFB-LD and the absorption edge wavelength of the EA modulator. As described above, the oscillation wavelength λ (lambda) of the DFB-LD has a dependency of about 0.1 nm / ° C. On the other hand, the absorption edge wavelength Λ (large lambda) of the EA modulator has a temperature dependency of about 0.6 nm / ° C. The detuning amount ΔH (= λ−Λ) defined by these differences is an important parameter that determines the characteristics of the EA / DFB element, and has a temperature dependency of about −0.5 nm / ° C.

  FIG. 3 is a diagram for explaining the element temperature dependency of the current-optical output (IL) characteristics of the DFB-LD unit. FIG. 3 shows the results of measuring the current-light output (IL) characteristics using the temperature as a parameter for a DFB-LD unit that is cut off by cleavage of the EA modulator. Here, T1 <T2 <T3 <T4. As can be seen from FIG. 3, as the element temperature rises, the threshold current (x-axis intercept of the curve) at which laser oscillation starts increases and the optical power decreases.

  On the other hand, regarding the EA modulator, the element temperature dependence of the static extinction ratio (DCER) characteristic and the small signal α parameter (alpha parameter: chirping parameter) will be described. Here, FIG. 4 is a diagram for explaining the element temperature dependency of the static extinction ratio (DCER) characteristic. FIG. 5 is a diagram for explaining the element temperature dependence of the small signal α parameter. 4 and 5, the horizontal axis represents the reverse voltage applied to the EA modulator section. As the element temperature rises, the detuning amount ΔH decreases and the absorption in the EA modulator section increases, so that DCER decreases. Similarly, as the element temperature rises, the detuning amount ΔH decreases and the absorption in the EA modulator section increases, so the small signal α parameter decreases.

  When the element temperature is changed to match the wavelength channel for DWDM, it is necessary to have substantially the same modulation characteristics and transmission characteristics in the temperature range. First, in order to obtain approximately the same optical output during modulation, the operating current of the DFB-LD must be varied. Specifically, as the temperature increases, the optical output of the DFB-LD itself decreases, and the basic absorption amount (absorption amount when the reverse voltage applied to the EA modulator is zero) decreases the detuning amount ΔH. In consideration of the increase along with this, it is necessary to vary the operating current from Iop1 to Iop4 as indicated by black dots in each curve of FIG. That is, the higher the temperature, the more optical output of the DFB-LD is necessary.

  In the EA modulator section, in order to reduce the temperature dependence of the detuning amount ΔH, the reverse direction applied voltage is changed depending on the temperature. That is, when a reverse voltage is applied to the EA modulator due to the quantum confined Stark effect, the absorption spectrum of the EA modulator section is shifted to the longer wavelength side, and the detuning amount ΔH is artificially reduced. FIG. 6 is a diagram for explaining that the reverse voltage applied to the EA modulator is changed to correct the detuning amount ΔH so as to be constant at each temperature. FIG. 6 also shows the characteristics of FIG. 3, and the temperature dependence of the detuning amount ΔH is reduced by increasing the reverse applied voltage as the temperature decreases. Thus, in order to make the modulation / transmission characteristics of the EA modulator the same at each temperature, it is important to first make correction so that ΔH becomes substantially constant.

  Further, as shown in FIG. 4, the saturation extinction ratio in the static extinction characteristic becomes smaller as the temperature becomes lower. Therefore, in order to make the dynamic extinction ratio (ACER) substantially constant at each temperature, It is necessary to increase the amplitude of the high frequency voltage to be operated. In FIG. 4, in order to obtain a certain ACER, a large reverse voltage Vb1 and a large amplitude voltage Vpp1 are required at a low temperature (T1). On the other hand, at high temperature (T4), a small reverse voltage Vb4 and a small amplitude voltage Vpp4 are sufficient.

  On the other hand, with respect to the small signal α parameter, as shown in FIG. 5, when the same reverse applied voltage and amplitude voltage are given, an approximately equal α curve can be cut out at the temperature. That is, the α value at the reverse voltage Vb1 at the low temperature (T1) and the α value at the reverse voltage Vb4 at the high temperature (T4) are substantially the same. Also, the α value at the voltage that is the sum of the reverse voltage Vb1 and the amplitude voltage Vpp1 at the low temperature (T1) and the α value at the voltage that is the sum of the reverse voltage Vb4 and the amplitude voltage Vpp4 at the high temperature (T4). It is almost the same. Therefore, a desired distance can be transmitted at any temperature.

  Hereinafter, a description will be given of a result obtained by driving at 40 Gbit / s and transmitting 40 km in an EA / DFB element using indium gallium arsenide phosphorus (InGaAsP) MQW as an active layer of the EA modulator section. At this time, the device was operated at an element temperature of 15 ° C. to 55 ° C., that is, over a wavelength range of about 4 nm. FIG. 7 is a diagram illustrating the result of obtaining the drive current Iop of the DFB-LD so as to satisfy substantially the same modulation characteristics and transmission characteristics at each temperature. FIG. 8 is a diagram for explaining the result of obtaining the reverse voltage Vb applied to the EA modulator so as to satisfy substantially the same modulation / transmission characteristics at each temperature. FIG. 9 is a diagram for explaining the results of obtaining the voltage amplitude Vpp of the high-frequency signal so as to satisfy substantially the same modulation / transmission characteristics at each temperature. In any figure, it is a substantially linear characteristic in the temperature range of 15 degreeC to 55 degreeC. Therefore, if these characteristics are recorded in the EA modulator control circuit 115 and the laser drive current control circuit 116 in FIG. 1 and the EA modulator driver 111 and the laser drive current driver 112 are controlled, a temperature range of 15 ° C. to 55 ° C. , Almost the same modulation characteristics and transmission characteristics can be obtained.

FIG. 10 summarizes the optimum driving conditions and the results of modulation / transmission characteristics obtained by actual measurement when the above-described wavelength tunable optical transmitter is driven at a transmission speed of 10 Gbit / s and transmitted at 40 km. These are optimum characteristics that can be obtained by finely adjusting the approximate driving conditions examined over a wide temperature range in the state of the element. Here, FIG. 10 is a diagram for explaining the oscillation wavelength, driving conditions, modulation characteristics, and transmission characteristics at each temperature. In FIG. 10, T
201 is the EA / DFB element temperature, Iop 202 is the DFB-LD drive current at that temperature, Vb 203 is the reverse applied voltage of the EA modulator, Vpp 204 is the high frequency amplitude voltage of the EA modulator, and λ 205 is the oscillation wavelength at that temperature, The ITU-T standard wavelength channel 206 is a corresponding channel number, ACER 207 is a dynamic extinction ratio of modulation characteristics, and Pp 208 is a path penalty of transmission characteristics. As shown in FIG. 10, the characteristics satisfying the ITU-T standard can be obtained in the 6 wavelength channel.

  In the present embodiment, the laser unit of the semiconductor optical element mounted on the wavelength tunable laser module determines the driving condition as a DFB-LD. Even in the case of the DBR-LD, the temperature dependence of the oscillation wavelength is the same as that of the DFB-LD. Therefore, those skilled in the art will recognize that when mounted on the wavelength tunable laser module, the driving conditions can be determined in the same manner. The same applies to the other embodiments.

  In addition, the semiconductor laser applied to this example is a semiconductor laser that oscillates in a single longitudinal mode having a submode suppression ratio of 30 dB or more (more preferably 35 dB or more). Furthermore, the temperature control range may be narrowed to 20 ° C. to 50 ° C., and the width of the variable wavelength range may be set to 3 nm to further stabilize the characteristics.

  FIG. 11 is a diagram for explaining the band structures of InGaAsP-based MQW and InGaAlAs-based MQW. The InGaAsP-based MQW shown in FIG. 11A is characterized by a large band offset ΔEv in the valence band and a small band offset ΔEc in the conduction band. In addition, the InGaAlAs-based MQW shown in FIG. 11B is characterized in that ΔEv is small and ΔEc is large. In the EA modulator composed of InGaAsP-based MQW, electrons can be sufficiently confined when the well is deep, but the hole confinement is weakened with the aim of improving the chirping characteristics, that is, reducing the small signal α parameter. Then, confinement of electrons with a light effective mass is not sufficient, and the extinction ratio, which is the ratio of light on / off, is deteriorated. On the other hand, in the EA modulator composed of InGaAlAs-based MQW, as shown in the comparison of FIG. 11, even if the hole confinement is weakened and the chirping characteristics are improved, the electron confinement can be sufficiently strengthened. It is possible to obtain an extinction ratio.

  In addition, when the element temperature is lowered, the saturation extinction ratio of the static extinction ratio is generally reduced, so that the dynamic extinction ratio tends to be small. However, in the InGaAlAs-based MQW, due to the characteristics of the band structure described above, Nevertheless, it is possible to obtain a sufficient dynamic extinction ratio. In addition, in the case of a DFB-LD made of InGaAlAs MQW, electrons are confined more strongly and holes are uniformly injected compared to a DFB-LD made of InGaAsP MQW. Stable operation over a wide range of temperatures is possible. However, the semiconductor material used for the active layer of the DFB-LD is an InGaAsP-based material if the required optical output power can be obtained in a wide temperature range even if the optical power is finally absorbed to some extent by the EA modulator. Either MQW or InGaAlAs MQW may be used. Thus, the use of InGaAlAs-based MQW for the active layer is a very effective means for improving the characteristics. The EA / DFB element composed of InGaAlAs-based MQW differs from that composed of InGaAsP-based MQW only in the semiconductor material used. For this reason, an EA / DFB element composed of InGaAlAs-based MQW can be manufactured without any deterioration in yield by only slightly changing the manufacturing process such as an etching solution or a pretreatment method for crystal growth.

  Hereinafter, a description will be given of a result of driving at a transmission rate of 10 Gbit / s and transmitting at 80 km in an optical transmitter in which an EA / DFB element using InGaAlAs-based MQW is mounted on the active layer of the EA modulator section. At this time, the device was operated over an element temperature of −5 ° C. to 85 ° C., that is, a wavelength range of about 9 nm. Here, FIG. 12 is a diagram for explaining the result of obtaining the drive current Iop of the DFB-LD so as to satisfy substantially the same modulation / transmission characteristics at each temperature. FIG. 13 is a diagram for explaining the result of obtaining the reverse voltage Vb applied to the EA modulator so as to satisfy substantially the same modulation / transmission characteristics at each temperature. FIG. 14 is a diagram for explaining the result of obtaining the voltage amplitude Vpp of the high-frequency signal so as to satisfy substantially the same modulation characteristics and transmission characteristics at each temperature. In any figure, it is a substantially linear characteristic in the temperature range of -5 degreeC to 85 degreeC. Therefore, if these characteristics are recorded in the EA modulator control circuit 115 and the laser drive current control circuit 116 in FIG. 1 and the EA modulator driver 111 and the laser drive current driver 112 are controlled, a temperature of −5 ° C. to 85 ° C. In the range, almost the same modulation characteristics and transmission characteristics can be obtained.

  FIG. 15 summarizes the optimum drive conditions and the results of modulation / transmission characteristics when this wavelength tunable optical transmitter is driven at a transmission speed of 10 Gbit / s and transmitted at 80 km. Here, FIG. 15 is a diagram for explaining the oscillation wavelength, drive conditions, and transmission characteristics at each temperature. The description of each column in FIG. 15 is the same as in FIG. 10, but since an EA / DFB element using InGaAlAs-based MQW is mounted, the usable temperature range is wide, and the wavelength is variable in the range of 12 wavelength channels. An optical transmitter could be obtained. As shown in FIG. 15, a characteristic satisfying the ITU-T standard was obtained in the 12 wavelength channel.

  With reference to FIG. 16, an optical transceiver according to another embodiment will be described. Here, FIG. 16 is a block diagram of an optical transceiver. In FIG. 16, a plurality of low-bit-rate electric signals are converted into electric signals with a transmission speed of 10 Gbit / s by a MUX (multiplexer) 904 and input to the EA modulator drive driver 111. The wavelength of the tunable laser module 109 is determined by a control line (not shown), and the temperature is controlled so that the oscillation wavelength becomes the same. The control temperature is transmitted to the drive control circuit 110, and by referring to a reference table (not shown) provided in the drive control circuit 110, the LD drive current, the reverse voltage of the EA modulator, and the high frequency amplitude voltage are obtained. The drive control circuit 110 sets these drive conditions in the EA modulator drive driver 111 and the laser drive current driver 112, respectively. The EA modulator drive driver 111 and the laser drive current driver 112 drive the EA modulator unit and the DFB-LD unit of the wavelength tunable laser module 109, respectively. As a result, in any variable wavelength channel, an optical signal having a transmission rate of 10 Gbit / s in which substantially the same modulation characteristics and transmission characteristics are ensured can be transmitted to the fiber 200-1.

  On the other hand, an optical signal having a transmission rate of 10 Gbit / s from the fiber 200-2 is OE converted by the optical receiving module 906, amplified by the amplifier 907, and then a plurality of low bit rate electric signals by the DEMUX (demultiplexer) 908. The signal is demultiplexed.

  In the present embodiment, a wavelength tunable optical transmitter in which the driving conditions of the DFB-LD and the EA modulator are defined in each wavelength channel described in the first and second embodiments is incorporated in the optical transceiver. As a result, a compact and low-cost optical transmitter / receiver capable of transmitting 40 km or 80 km at a transmission rate of 10 Gbit / s and variable in wavelength of 6 channels or 12 channels at a wavelength interval of 0.8 nm can be realized. In this specification, the optical transmitter includes an optical transceiver.

  100 wavelength tunable optical transmitter, 101 EA / DFB element, 102 chip carrier, 103 Peltier substrate, 104 thermistor, 105 high frequency amplitude controller, 106 wavelength locker module, 107 beam splitter, 108 focusing lens, 109 wavelength tunable laser module Package, 110 Drive control circuit, 111 EA modulator drive driver, 112 Laser drive current driver, 113 Reverse voltage controller, 114 Peltier temperature control circuit, 115 EA modulator control circuit, 116 Laser drive current control circuit, 117 Monitor photo Diode, 900 wavelength variable optical transceiver, 904 MUX (multiplexer), 906 optical receiver module, 907 amplifier, 908 DEMUX (demultiplexer).

Claims (10)

An electroabsorption modulator integrated laser in which the electroabsorption modulator and the semiconductor laser are integrated on the same semiconductor substrate;
A temperature control circuit for varying the temperature of the electroabsorption modulator integrated laser;
A laser driving section for driving the semiconductor laser;
A modulator driver for driving the electroabsorption modulator;
A drive control circuit for controlling the laser driver and the modulator driver;
With
The temperature control circuit makes the oscillation wavelength of the electroabsorption modulator integrated laser variable in a wavelength range of 3 nm or more by changing the temperature of the electroabsorption modulator integrated laser,
The drive control circuit includes a relationship between a drive current and temperature applied to the semiconductor laser, a reverse voltage and temperature applied to the electroabsorption modulator, and a high-frequency amplitude voltage applied to the electroabsorption modulator. Record the relationship between temperature and temperature,
The drive control circuit controls the laser drive unit and the modulator drive unit on the basis of the recorded relationship, and the laser drive unit and the laser drive unit and the transmission characteristic are substantially the same in the wavelength range. Driving the semiconductor laser and the electroabsorption modulator to the modulator driver,
A tunable transmitter characterized by the above. An electroabsorption modulator integrated laser in which the electroabsorption modulator and the semiconductor laser are integrated on the same semiconductor substrate;
A temperature control circuit for varying the temperature of the electroabsorption modulator integrated laser;
A laser driving section for driving the semiconductor laser;
A modulator driver for driving the electroabsorption modulator;
A drive control circuit for controlling the laser driver and the modulator driver;
With
The temperature control circuit controls the temperature of the electroabsorption modulator integrated laser in a temperature range of a temperature difference of 30 ° C. or more;
The drive control circuit includes a relationship between a drive current and temperature applied to the semiconductor laser, a reverse voltage and temperature applied to the electroabsorption modulator, and a high-frequency amplitude voltage applied to the electroabsorption modulator. Record the relationship between temperature and temperature,
The drive control circuit controls the laser drive unit and the modulator drive unit based on the recorded relationship, and the laser drive unit has substantially the same modulation characteristics and transmission characteristics in the temperature range. And driving the semiconductor laser and the electroabsorption modulator to the modulator driving unit,
A tunable transmitter characterized by the above. The wavelength tunable transmitter according to claim 1 or 2,
The electro-absorption modulator includes a multiple quantum well made of indium gallium aluminum arsenide. The wavelength tunable transmitter according to claim 1 or 2,
The electro-absorption modulator includes a multiple quantum well made of indium gallium arsenide phosphorus. The wavelength tunable transmitter according to any one of claims 1 to 4,
The wavelength tunable transmitter, wherein the semiconductor laser is a distributed feedback laser or a distributed reflection laser. A wavelength tunable transmitter according to any one of claims 1 to 5,
The wavelength tunable transmitter, wherein the electroabsorption modulator integrated laser operates at a transmission speed of 2.5 Gbit / s or more. The wavelength tunable transmitter according to any one of claims 1 to 6,
When the temperature of the electroabsorption modulator integrated laser rises, the drive control circuit increases the drive current applied to the semiconductor laser to the laser drive unit, and the electroabsorption is controlled by the temperature of the modulator integrated laser. When the voltage drops, the drive current applied to the semiconductor laser is reduced in the laser drive unit.
A tunable transmitter characterized by the above. The wavelength tunable transmitter according to any one of claims 1 to 7,
The drive control circuit reduces the reverse voltage and the high-frequency amplitude voltage applied to the electroabsorption modulator in the modulator drive section when the temperature of the electroabsorption modulator integrated laser rises. When the temperature of the electroabsorption modulator integrated laser is lowered, and to the modulator driver, the reverse voltage applied to the electroabsorption modulator and the voltage of the high frequency amplitude are increased.
A tunable transmitter characterized by the above. A wavelength tunable transmitter according to any one of claims 1 to 8,
A chip carrier on which the electroabsorption modulator integrated laser is mounted;
A Peltier element mounted with the chip carrier,
The temperature control circuit varies the temperature of the electroabsorption modulator integrated laser by controlling the Peltier element.
A tunable transmitter characterized by the above. A wavelength tunable transmitter according to any one of claims 1 to 9,
An optical receiver including an optical receiver module that converts the received optical signal into an electrical signal;
An optical transceiver.

Images