JP2017118052A - Wavelength multiplex optical transmitter and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength multiplex optical transmitter which can feed back both a DFB laser and a SOA while monitoring them simultaneously, and can perform good APC operation, and to provide a control method therefor.SOLUTION: In a wavelength multiplex optical transmitter including a plurality of SOA integration EA-DFB including a DFB laser and an EA modulator and a SOA, and an optical multiplexer outputting wavelength multiplex light by multiplexing multiple signal lights emitted from respective SOAs, the oscillation wavelength of the DFB laser and the gain of the SOA of the DFB laser in the plurality of SOA integration EA-DFB are different from each other. In each of the plurality of SOA integration EA-DFB, the DFB laser and the SOA are driven by a single control terminal, and the wavelength multiplex optical transmitter further includes a current monitor connected with the EA modulators of the plurality of SOA integration EA-DFB, and monitoring the light receiving current generated in the EA modulator.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a wavelength division multiplexing optical transmitter and a control method for monitoring and controlling the optical intensity, and more particularly, an EA modulator integrated DFB laser (Electroabsorption Modulator) integrated with a semiconductor optical amplifier (SOA). The present invention relates to a wavelength multiplexing optical transmitter including an Integrated Distributed Feedback Laser (EA-DFB laser) and a control method thereof.

  With the spread of optical communication, in the metro optical communication network that connects relay stations between cities, the communication speed is increasing from 10 Gbit / s to 25 Gbit / s, and further 40 Gbit / s. For example, in the case of 10 Gbit / s, long-distance transmission of single mode fiber (SMF) 40 to 80 km transmission is required in this metro optical communication network (the required transmission distance is usually the square of the bit rate (modulation speed)). However, miniaturization, low power consumption, and low chirp of optical transmission modules are important issues.

  In general, in order to perform high-speed and long-distance transmission as described above, an external modulation method with small chirping is used. Among these, an electroabsorption (EA) modulator utilizing an electroabsorption effect has excellent features from the viewpoints of downsizing, low power consumption, and integration with a semiconductor laser. In particular, a semiconductor optical integrated device (EA-DFB laser) in which an EA modulation device and a distributed feedback laser (DFB) laser excellent in single wavelength property are monolithically integrated on one semiconductor substrate is high speed and long. Widely used as a light transmission device for distance transmission, the signal light wavelength is mainly a 1.5 μm band with a small optical fiber propagation loss or a 1.3 μm band with a small chirp.

  In general, optical communication requires that the optical intensity of an optical transmission signal be kept constant. Therefore, conventionally, a part of the optical transmission signal is branched, the light intensity is monitored, and the current injected into the DFB laser is controlled so that the monitored light intensity is constant. This is called APC (auto power control).

  FIG. 1 is a diagram for explaining a conventional light intensity monitoring method for performing APC. In the optical module 100 shown in FIG. 1, a DC drive current is applied to the DFB laser unit 110, and a bias voltage and an RF (signal) voltage are applied to the EA modulator unit 120 via a bias T. As a result, the light output from the DFB laser unit 110 is modulated by the EA modulator unit 120 and output as modulated light. The modulated light output from the EA modulator unit 120 is converted into parallel light by the lens 131, collected by the lens 132, and input to the optical fiber 133. Here, a part of the parallel light is branched by the mirror 134 and received by the light receiver 135, whereby the change in the light intensity of the modulated light can be monitored. When the light intensity decreases, feedback is performed so as to increase the drive current of the DFB laser unit 110, and when the light intensity increases, feedback is performed so that the drive current decreases, thereby enabling APC.

  In FIG. 1, the branching mirror 134 is provided before the modulated light is input to the optical fiber 133, but the modulated light is branched by a part of the modulated light after being input to the optical fiber 133 by the optical coupler. It is also possible to monitor changes in the light intensity.

  Further, development of 100 Gigabit Ethernet (100 GbE) is progressing as one of the standards constituting the next-generation ultra-high speed network (see Non-Patent Document 2). In particular, 100GBASE-LR4 and 100GBASE-ER4 that exchange data between medium and long distance buildings (-10 km) and remote buildings (-40 km) are promising. In the above-mentioned standard, four wavelengths (for example, 1294.53 nm to 1296.59 nm, 1299.02 nm to 1301.09 nm, 1303.54 nm to 1305.63 nm, and 1308.09 nm to 1310.19 nm) are defined. ), A LAN-WDM method is used in which 25 Gb / s (or 28 Gb / s) data is placed on each of the data and then superimposed to generate a 100 Gb / s signal. In LAN-WDM, a wavelength division multiplexing optical transmitter module is used.

  Next, another configuration of a conventional light intensity monitoring method for performing APC in such LAN-WDM will be described with reference to FIG. FIG. 2 shows a configuration of a conventional wavelength multiplexing optical transmitter module used at 100 GbE. FIG. 2 shows a wavelength division multiplexing optical transmitter module 200 that includes a wavelength division multiplexing optical transmitter 210 that is one semiconductor chip and a spatial optical system 220 and is connected to an optical fiber 230. The wavelength multiplexing optical transmitter 210 and the optical fiber 230 are optically coupled via the spatial optical system 220.

Wavelength multiplexing optical transmitter 210 includes a EA-DFB211 ₀ ~211 _3, and the light receiver 212 _{0-212 3} for EA-DFB211 ₀ ~211 ₃ monitors, one of the multimode interference (MMI) type 4-one Of the optical multiplexer 216, input waveguides 215 _{0 to} 215 _{3 for} connecting the EA-DFBs 211 _{0 to} 211 ₃ and the optical multiplexer 216, respectively, and an output waveguide 217 of the optical multiplexer 216. In the EA-DFBs 211 _{0 to} 211 ₃ , DFB lasers 213 _{0 to} 213 ₃ and EA type optical modulators 214 _{0 to} 214 ₃ are integrated, respectively.

The DFB lasers 213 _{0 to} 213 ₃ all output continuous light, and the laser oscillation wavelength bands of the DFB lasers 213 _{0 to} 213 ₃ are 1294.53 nm to 1296.59 nm, 1299.02 nm to 1301.09 nm, and 1303, respectively. .54 nm to 1305.63 nm, 1308.09 nm to 1310.19 nm. Here, the four wavelength bands are generally referred to as lane 0, lane 1, lane 2, and lane 3 from the short wavelength side.

The EA type optical modulators 214 _{0 to} 214 ₃ have absorption layers of the same composition, and the continuous light of the DFB lasers 213 _{0 to} 213 ₃ is 25 Gb according to the electric inputs of different electric signals (25 Gb / s or 28 Gb / s). / S or 28 Gb / s modulated signal light. Modulated optical signal generated by the EA optical modulator 214 _{0-214 3} are outputted through the input waveguide 215 _{0-215 3} to the optical multiplexer 216.

The optical multiplexer 216 multiplexes four modulated signal lights having different wavelengths respectively input from the EA-DFBs 211 _{0 to} 211 ₃ and combines them into a single wavelength multiplexed light via the output waveguide 217 as a spatial optical system. To 220.

  The spatial optical system 220 includes a first lens 221, an isolator 222, and a second lens 223. The wavelength multiplexed light that is bundled and output by the optical multiplexer 216 is emitted into the space as diffused light 240, is converted into parallel light 241 by the first lens 221, passes through the isolator 222, The convergent light 242 is condensed by the second lens 223 and coupled to the optical fiber 230.

Although not shown in the figure, the wavelength multiplexing optical transmitter module 200 includes a temperature sensor (for example, thermistor) of the wavelength multiplexing optical transmitter 210, a Peltier element for temperature control, and DFB lasers 213 _{0 to} 213 in addition to the above. ₃ and EA optical modulator 214 _{0-214 3} power can have a DC power supply for supplying. The wavelength multiplexing optical transmitter module 200, the modulator driver transmission line termination resistors for driving the EA optical modulator 214 _{0-214 3,} controls the amplitude and bias voltage and electrical cross-point of the modulator driver A signal line and a control circuit can be provided. Further, in the wavelength division multiplexing optical transmitter module 200, an electrical signal waveform shaping circuit, a clock extraction circuit, and a circuit for suppressing the influence of power supply voltage fluctuations may be provided in front of the modulator driver.

The EA optical modulator 214 _{0-214 3,} excellent extinction ratio, also the hole in the pile-up suppression can be used effective InGaAlAs system tensile strained quantum well. As the input waveguides 215 _{0 to} 215 ₃ and the output waveguide 217, a ridge type waveguide embedded with a low dielectric constant BCB can be used in order to secure a high frequency band. As the optical multiplexer 216, a high-mesa waveguide with strong optical confinement and small radiation loss can be used.

The chip size of the wavelength multiplexing optical transmitter 210 can be set to, for example, 2,000 × 2,600 μm, the resonance lengths of the four DFB lasers 213 _{0 to} 213 ₃ are 400 μm, and the DFB lasers 213 _{0 to} 213 ₃ are the waveguide length between the EA optical modulator 214 _{0-214 3} can be a 50 [mu] m, the device length of the EA optical modulator 214 _{0-214 3} may be 150 [mu] m.

  The wavelength division multiplexing optical transmitter module 200 is obtained by mounting the manufactured wavelength division multiplexing optical transmitter 210 in an ultra-small package of 12 mm × 20 mm. When operated at 100 Gbit / s at 40 ° C., it is 40 km on a single mode fiber. Error-free transmission is possible. As these results indicate, the wavelength division multiplexing optical transmitter module 200 has sufficient performance as a transceiver for a future generation of 100 GbE.

When APC is performed in a configuration in which modulated light of a plurality of wavelengths as shown in FIG. 2 is combined, a part of the modulated light is branched / monitored between lenses 221 and 223 as shown in FIG. Becomes meaningless. That is, since a plurality of modulated lights are combined, even if a decrease in the modulated light is detected, it is impossible to know which DFB lasers 213 _{0 to} 213 ₃ are fed back. Therefore, provided the photodetector 212 _{0-212 3} for EA-DFB211 ₀ ~211 ₃ monitors the rear of the DFB laser 213 _{0-213 3,} it is necessary to perform the monitoring at the rear of the DFB laser 213 _{0-213 3} is there. The light receivers 212 _{0 to} 212 ₃ monitor the light intensity of the light output to the rear of each DFB laser 213 _{0 to} 213 ₃ (the DFB laser generally outputs the laser light to the front and simultaneously the laser light to the rear. The light intensity of the light toward the front and the light intensity of the light toward the rear are not necessarily the same, but there is a correlation, and when one becomes strong, the other becomes strong, and when one becomes weak, the other becomes weak. When the light intensity is lowered, feedback is performed so as to increase the driving current of the DFB laser 213, and when the light intensity is increased, feedback is performed so that the driving current of the DFB laser 213 is decreased. APC is enabled in the instrument module 200.

  FIG. 3 is a cross-sectional view of a semiconductor chip formed with a light receiver, a DFB laser, an EA modulator, and a waveguide / optical multiplexer used in the wavelength division multiplexing optical transmitter 210 shown in FIG. 3 includes an n-electrode 301, an n-InP substrate 302 provided on the n-electrode 301, and an n-InP cladding layer 303 provided on the n-InP substrate 302, and includes an n-InP cladding layer. A semiconductor chip in which a light receiver 320, a DFB semiconductor laser 330, an EA modulator 340, and a waveguide / optical multiplexer 350 are provided on 303 is shown.

  The DFB semiconductor laser unit 330 includes an active layer 304 provided on the n-InP clad layer 303, a guide layer 305 provided on the active layer 304, and a p-InP clad layer 306 provided on the guide layer 305. And an electrode 307 provided on the p-InP clad layer 306. A diffraction grating is formed on the guide layer 305 by EB (electron beam) drawing.

  The EA modulator unit 340 includes an absorption layer 308, a p-InP cladding layer 306 provided on the absorption layer 308, and an electrode 309 provided on the p-InP cladding layer 306. The waveguide / optical multiplexer unit 350 includes a core layer 310 of a waveguide (or an optical multiplexer) and a non-doped InP layer 311.

  In the central portion of the DFB semiconductor laser unit 330, a quarter wavelength phase shift 312 is provided by phase shifting the diffraction grating by a quarter wavelength in order to realize a single mode of the oscillation wavelength. In one semiconductor chip, the composition of the active layer 304 is the same, and the wavelength is changed by changing the pitch of the diffraction grating. Further, the composition of the absorption layer 308 of the EA modulator is the same in one semiconductor chip.

  A light receiver section 320 is provided behind the DFB semiconductor laser section 330. The light receiver section 320 includes a light receiving layer 313, an upper clad layer 314, and an electrode 315 provided on the n-InP clad layer 303. Is configured. Here, normally, the light receiving layer 313 has the same composition as the core layer 310 and the upper cladding layer 314 has the same composition as the InP layer 311, but the light receiving layer 313 has the absorption layer 308 and the upper cladding layer 314 has the p-InP cladding layer 306. If the same composition may be used, the light receiving layer 313 may have the same composition as the active layer 304 and the guide layer 305.

JP 2013-258336 A

Tsuyoshi Fujisawa, Ji Kanazawa, Hiroyuki Ishii, Yasuhiro Kawaguchi, Nobuhiro Nuoya, Aki Ohki, Kiyoto Takahata, Ryuzo Iga, Fumiyoshi Kano, Hiromi Ohashi, "Monolithic Integrated Light Source for Next Generation 100GbE Transceivers" IEICE , November 2011, OCS2011-68, OPE2011-106, LQE2011-10, pp.77-80

  Although the conventional wavelength division multiplexing optical transmitter module shown in FIG. 1 and the conventional integrated wavelength division multiplexing optical transmitter module shown in FIG. 2 are useful, the problem of chirping remains. In order to solve the problem of chirping, there is a structure in which a semiconductor optical amplifier (SOA) is further integrated in an EA-DFB as shown in FIG. 4 (see, for example, Patent Document 1).

  In such SOA integrated EA-DFB, the length of the SOA is usually about 1/6 of that of the DFB laser, and the composition of the SOA and the composition of the DFB laser are the same (however, the SOA has a diffraction grating) Not) In the SOA integrated EA-DFB, in order to prevent an increase in the number of control terminals, the same terminal is used to control the DFB laser unit and the SOA unit to inject respective currents (currents flowing in the SOA and the DFB laser are SOA And distributed by the resistance ratio of the DFB laser). By using the SOA integrated EA-DFB shown in FIG. 4, the problem of chirping can be solved and the modulated light can be amplified by the SOA.

FIG. 5 is a diagram showing a configuration in which the SOA integrated EA-DFB shown in FIG. 4 is applied to the configuration of the LAN-WDM shown in FIG. In the configuration shown in FIG. 5, SOAs 418 _{0 to} 418 ₃ are added to the EA-DFBs 211 _{0 to} 211 ₃ shown in FIG. 2 to configure SOA integrated EA-DFBs 411 _{0 to} 411 ₃ . Although not shown, in the configuration shown in FIG. 5, the DFB laser 413 ₀ and the SOA 418 ₀ , the DFB laser 413 ₁ and the SOA 418 ₁ , the DFB laser 413 ₂ and the SOA 418 ₂ , the DFB laser 413 ₃ and the SOA 418 ₃ are respectively connected from the same terminal. A drive current is supplied.

Each photodetector 412 _{0-412 3} performs monitoring of light intensity of the light output in the DFB laser 413 _{0-413 3} backward (photodetector 412 side). When the monitored light intensity decreases, feedback is performed so as to increase the drive current of the SOA integrated EA-DFBs 411 _{0 to} 411 ₃ , and when the light intensity increases, APC can be performed by applying feedback so as to decrease the drive current. .

  According to the configuration shown in FIG. 5, since the elements can be arranged with the accuracy of the stepper by arraying them on the same wafer, the mounting can be simplified and the mounting yield can be increased as compared with arranging the individual elements. Also, in the method of arranging individual elements, it is impractical to arrange eight individual elements when considering using 400G 8 waves (8 wavelengths of 50 Gb / s) as a future purpose. Therefore, it is difficult to achieve the object, but the object can be achieved by using the configuration shown in FIG.

  FIG. 6 is a cross-sectional view of a semiconductor chip in which a light receiver, a DFB laser, an EA modulator, an SOA, and a waveguide / optical multiplexer are formed according to the configuration shown in FIG. The semiconductor structure shown in FIG. 6 corresponds to a structure in which an SOA part is added between the EA modulator part 340 and the waveguide / optical multiplexer part 350 of the semiconductor structure shown in FIG. As shown in FIG. 6, the SOA part 560 is configured by providing an active layer 561, a guide layer 562, and an electrode 563 on an n-InP cladding layer 503. A bias T is connected to the electrode 509 of the EA modulator section 540. The active layer 561 can be configured with the same composition as the active layer 504, and the guide layer 562 can be configured with the same composition as the guide layer 505.

However, in the configuration shown in FIG. 5, each of the light receivers 412 _{0 to} 412 ₃ can only monitor the DFB lasers 413 _{0 to} 413 ₃ , while feedback is provided to both the DFB lasers 413 _{0 to} 413 ₃ and the SOAs 418 _{0 to} 418 ₃ . It takes. Accordingly, when the SOAs 418 _{0 to} 418 ₃ are deteriorated and the amplification factors of the SOAs 418 _{0 to} 418 ₃ are lowered, the light output intensity is reduced as a result, but feedback is not applied. There was a problem that APC did not work well.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to monitor both the DFB laser and the SOA and establish APC feedback.

  A wavelength division multiplexing optical transmitter according to an embodiment of the present invention includes a plurality of SOA integrated EA-DFBs, each of which includes a DFB laser, an EA modulator connected to the DFB laser, and the EA modulator. And a plurality of SOA integrated EA-DFBs, and an optical multiplexer for combining the plurality of signal lights emitted from each of the plurality of SOA integrated EA-DFBs and outputting wavelength multiplexed light And a plurality of SOA integrated EA-DFBs, wherein the oscillation wavelength of the DFB laser and the SOA gain are different from each other, and in each of the plurality of SOA integrated EA-DFBs, The DFB laser and the SOA are driven by a single control terminal, and the wavelength multiplexing optical transmitter is connected to the EA modulators of the plurality of SOA integrated EA-DFBs. And further comprising a current monitor for monitoring the photocurrent generated in the EA modulator.

  The wavelength division multiplexing optical transmitter according to an embodiment of the present invention is the wavelength division multiplexing optical transmitter according to claim 1, wherein the single control is performed based on a monitoring result of the received light current in the current monitor. The drive current to the DFB laser driven by the terminal and the SOA is adjusted.

  A wavelength division multiplexing optical transmitter according to another embodiment of the present invention includes a plurality of SOA integrated EA-DFBs, a light receiver, a DFB laser connected to the light receiver, and an EA connected to the DFB laser. A plurality of SOA integrated EA-DFBs including a modulator and an SOA connected to the EA modulator, and a plurality of signal lights emitted from each of the SOAs of the plurality of SOA integrated EA-DFBs are combined. And a wavelength multiplexing optical transmitter that outputs wavelength multiplexed light, and the oscillation wavelength of the DFB laser and the gain of the SOA in the plurality of SOA integrated EA-DFBs are different from each other, In each of the plurality of SOA integrated EA-DFBs, the DFB laser and the SOA are driven by a single control terminal, and the photoreceiver is output to the photoreceiver side of the DFB laser. And performing monitoring of light intensity of the light.

  A wavelength division multiplexing optical transmitter according to another embodiment of the present invention is the wavelength division multiplexing optical transmitter according to claim 3, wherein the single wavelength is based on a monitoring result of the light intensity in the light receiver. A drive current to the DFB laser and the SOA driven by a control terminal is adjusted.

  According to the present invention, a wavelength division multiplexing optical transmitter capable of monitoring both a DFB laser and an SOA at the same time and applying feedback to both the DFB laser and the SOA and capable of performing a good APC operation and a control method thereof are provided. be able to.

It is a figure explaining the monitoring method of the conventional light intensity for performing APC. It is a figure which shows the structure of the conventional wavelength division multiplexing optical transmitter module used by 100 GbE. It is sectional drawing of the semiconductor chip in which the light receiver, DFB laser, EA modulator, and the waveguide and the optical multiplexer were formed. It is a figure which shows the structure which integrated SOA in the EA-DFB laser. It is a figure which shows the structure which applied SOA integrated EA-DFB to the structure shown in FIG. FIG. 6 is a cross-sectional view of a semiconductor chip on which a light receiver, a DFB laser, an EA modulator, an SOA, and a waveguide / optical multiplexer are formed according to the configuration shown in FIG. 5. It is a figure which shows the structure of the wavelength multiplexing optical transmitter module using the wavelength multiplexing optical transmitter which concerns on this invention. It is sectional drawing of the wavelength division multiplexing optical transmitter shown in FIG.

  Hereinafter, the wavelength division multiplexing optical transmitter according to the present invention will be described in detail.

  FIG. 7 shows a configuration of a wavelength multiplexing optical transmitter module using the wavelength multiplexing optical transmitter according to the present invention. FIG. 7 shows a wavelength multiplexing optical transmitter module 600 that includes a wavelength multiplexing optical transmitter 610 that is one semiconductor chip and a spatial optical system 620 and is connected to an optical fiber 630. The wavelength multiplexing optical transmitter 610 and the optical fiber 630 are optically coupled via the spatial optical system 620.

The wavelength division multiplexing optical transmitter 610 includes an SOA integrated EA-DFB 611 _{0 to} 611 ₃ , one multimode interference (MMI) type 4 to 1 optical multiplexer 616, an SOA integrated EA-DFB 611 _{0 to} 611 _3, and an optical multiplexer. Input waveguides 615 _{0 to} 615 ₃ to which the wave filters 616 are connected, respectively, and an output waveguide 617 of the optical multiplexer 616 are included. In the SOA integrated EA-DFBs 611 _{0 to} 611 ₃ , DFB lasers 613 _{0 to} 613 ₃ , EA type optical modulators 614 _{0 to} 614 ₃ , and SOAs 618 _{0 to} 618 ₃ are integrated, respectively. The DFB lasers DFB lasers 613 _{0 to} 613 ₃ and SOAs 618 _{0 to} 618 ₃ are respectively driven by the same terminal. The structure of the wavelength multiplexing optical transmitter shown in FIG. 7 corresponds to the structure in which the light receivers 412 _{0 to} 412 ₃ are eliminated from the wavelength multiplexing optical transmitter 410 shown in FIG.

  FIG. 8 is a cross-sectional view of the wavelength division multiplexing optical transmitter 610 shown in FIG. As shown in FIG. 8, in the wavelength division multiplexing optical transmitter 610 according to the present invention, instead of eliminating the photoreceiver unit 520 from the structure shown in FIG. 6, between the electrode 709 of the EA modulator unit 740 and the input unit of the bias voltage. Is provided with a current monitor 770.

  Since a reverse bias is applied to the EA modulator unit 740, almost no current flows (for example, 0.01 mA or less) even when a bias voltage is applied when light is not input. On the other hand, since the EA modulator is a modulator that absorbs light (by increasing the loss) and modulates, the EA modulator unit 740 operates like a light receiver. That is, when light of a certain intensity (for example, 3 dBm) is input and a voltage for modulation (bias voltage + modulation voltage) is applied, the EA modulator unit 740 generates a light receiving current of about 10 mA, for example.

  The SOA unit 760 amplifies the light incident from behind (via the EA modulator from the DFB laser), and outputs the amplified light and amplified spontaneous emission (ASE) to the front. ASE is output to the rear. Therefore, both the output light from the DFB laser unit 720 and the ASE from the SOA unit 760 are input to the absorption layer 708 of the EA modulator unit 740.

  As described above, since the EA modulator unit 740 operates as a light receiver, the light reception current generated by the light reception is monitored by the current monitor 770 provided between the electrode 709 of the EA modulator unit 740 and the bias voltage input unit. Can do. APC feedback can be performed based on the monitoring result of the received light current. That is, for example, when the light receiving current increases (the light intensity increases), it is possible to control to decrease the drive currents of both the DFB laser unit 720 and the SOA unit 760.

  As a result, both the DFB laser unit 720 and the SOA unit 760 can be monitored at the same time, and feedback can be applied to both the DFB laser unit 720 and the SOA unit 760, so that a good APC operation is possible.

  In the present invention, four SOA integrated EA-DFBs and an example of an MMI type 4-to-1 optical multiplexer as an optical multiplexer have been described. However, the number of SOA integrated EA-DFBs and the number of branches of the optical multiplexer are as described above. Not caught. That is, the number of SOA integrated EA-DFBs may be, for example, 2, 8, 16, or more, and the optical multiplexer may be 2: 1, 8: 1, or 16: 1. The optical multiplexer is not limited to the MMI type, and may be a directional coupler, a Y branch, a Mach-Zehnder, a dielectric multilayer filter, an arrayed waveguide grating type, or a combination thereof.

Usually, the wavelength of each lane is
lane 0: 1294.53-1296.59 nm
lane 1: 1299.02-1301.09 nm
lane 2: 1303.54-1305.63 nm
lane3: 1308.009-1310.19nm
The modulation rate by the EA modulator is 25 Gb / s or 28 Gb / s, but the present invention is not limited to the above. This is because if the number of EA-DFBs changes, the number of lanes and the interval also change.

  Further, normally, the wavelength division multiplexing optical transmitter module is used at 25 Gb / s × 4 wavelengths = 100 Gb / s. For example, 50 Gb / s × 8 wavelengths = 400 Gb / s, 25 Gb / s × 16 wavelengths = 400 Gb / s, It may be used at 10 Gb / s × 10 wavelengths = 100 Gb / s. Furthermore, although the example which set lane0-3 in order from the top was demonstrated in the said Example, the order of lane is arbitrary and is not caught by the said description. In the above description, the length of the DFB laser, the length of the EA modulator, and the length of the SOA are assumed to be the same for each lane. However, the lengths may be different for each lane. In the above description, the composition of the DFB laser, the EA modulator, and the SOA is the same for each lane. However, the composition may be different for each lane.

  In the above description, the DFB laser, the EA modulator, the SOA, the waveguide, and the optical multiplexer are all provided on the same semiconductor substrate. However, the present invention is not limited to this. For example, a DFB laser, an EA modulator, and an SOA may be provided on the same semiconductor substrate, and the waveguide may be an optical multiplexer made of a silica-based waveguide or a silicon waveguide on a silicon substrate. Furthermore, the DFB laser, the EA modulator, and the SOA may not be on the same semiconductor substrate, but may be on different substrates.

Claims (4)

A plurality of SOA integrated EA-DFBs, comprising: a DFB laser; an EA modulator connected to the DFB laser; and an SOA connected to the EA modulator;
An optical multiplexer that combines a plurality of signal lights emitted from the SOAs of each of the plurality of SOA integrated EA-DFBs and outputs wavelength multiplexed light;
A wavelength division multiplexing optical transmitter comprising:
The oscillation wavelength of the DFB laser and the gain of the SOA in the plurality of SOA integrated EA-DFBs are different from each other,
In each of the plurality of SOA integrated EA-DFBs, the DFB laser and the SOA are driven by a single control terminal,
The wavelength division multiplexing optical transmitter further includes a current monitor connected to the EA modulators of the plurality of SOA integrated EA-DFBs for monitoring a received light current generated by the EA modulators. Wavelength multiplexed optical transmitter.   2. The wavelength division multiplexing optical transmitter according to claim 1, wherein a drive current to the DFB laser and the SOA driven by the single control terminal is adjusted based on a monitoring result of the received current in the current monitor. A method of controlling a wavelength division multiplexing optical transmitter. A plurality of SOA integrated EA-DFBs, comprising: a light receiver; a DFB laser connected to the light receiver; an EA modulator connected to the DFB laser; and an SOA connected to the EA modulator. Including a plurality of SOA integrated EA-DFBs;
An optical multiplexer that combines a plurality of signal lights emitted from the SOAs of each of the plurality of SOA integrated EA-DFBs and outputs wavelength multiplexed light;
A wavelength division multiplexing optical transmitter comprising:
The oscillation wavelength of the DFB laser and the gain of the SOA in the plurality of SOA integrated EA-DFBs are different from each other,
In each of the plurality of SOA integrated EA-DFBs, the DFB laser and the SOA are driven by a single control terminal,
The wavelength multiplex optical transmitter, wherein the light receiver monitors the light intensity of light output to the light receiver side of the DFB laser.   4. The wavelength division multiplexing optical transmitter according to claim 3, wherein a drive current to the DFB laser and the SOA driven by the single control terminal is adjusted based on a monitoring result of the light intensity in the light receiver. A method of controlling a wavelength division multiplexing optical transmitter.

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