Optical Transmitter

Abstract

To provide an optical transmitting apparatus that ensures bandwidth characteristics according to the baud rate of an optical signal.SOLUTION: An optical transmitting apparatus includes a conversion device that converts an electrical data signal into an optical signal, a control unit that changes an adjustment value of peaking based on the baud rate of the optical signal, and a driver that changes bandwidth characteristics of the conversion device based on the adjustment value changed by the control unit.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] This invention relates to an optical transmission device.

Background Art

[0002] There is known an optical transmission device that digitally processes a data signal for transmission used in a drive signal of an optical modulator to generate an optical signal having an arbitrary optical waveform (see, for example, Patent Document 1).

[0003] Also, there is known a technique of converting a data signal amplified by an optical modulator driver into an optical signal using a semiconductor laser element. The optical modulator driver may have a characteristic called peaking in which the frequency response characteristic is particularly high in a certain frequency band (see, for example, Patent Document 2). In addition, various techniques related to peaking are known (see, for example, Patent Documents 3 to 5).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, research is being conducted on optical transmission devices that utilize peaking to transmit optical signals at higher baud rates. For example, research is being conducted on transmitting optical signals at high baud rates, such as around 130 Gbaud, which are beyond the range of low baud rates like 64 Gbaud to medium baud rates like 96 Gbaud.

[0006] However, increasing the baud rate increases the spectral width, which may increase the amount of bandwidth constriction experienced within the ROADM (Reconfigurable Optical Add / Drop Multiplexer) installed in the optical transmission path.

[0007] From this perspective, it is preferable to realize an optical transmitting device that can not only transmit high-baud-rate optical signals but also support a wide range of baud rates, including low-baud-rate to medium-baud-rate optical signals.

[0008] Here, if the bandwidth characteristics of the optical transmitter are fixed to, for example, a bandwidth characteristic that allows the transmission of low-baud rate optical signals, the bandwidth characteristics of high-baud rate optical signals may be distorted by the set bandwidth characteristics, potentially degrading transmission performance. For this reason, it is assumed that the bandwidth characteristics of the optical transmitter will be fixed to a bandwidth characteristic that allows the transmission of high-baud rate optical signals. This makes it possible to transmit optical signals in the range from low to high baud rates without distortion.

[0009] However, when transmitting a low-baud rate optical signal while the bandwidth characteristics of the optical transmitter are fixed to a bandwidth characteristic that allows the transmission of high-baud rate optical signals, there are no (or very few) optical signal components in the region between the set bandwidth characteristics and the low-baud rate optical signal. On the other hand, noise components from the optical transmitter may remain in this region. In wavelength division multiplexing transmission, these noise components may degrade the signal quality of other optical signals adjacent to the optical signal. Thus, if the bandwidth characteristics of the optical transmitter are fixed to a bandwidth characteristic that allows the transmission of high-baud rate optical signals, the optical signal will not be distorted in wavelength division multiplexing transmission using low-baud rate optical signals, but the transmission performance may be degraded due to noise components.

[0010] Therefore, one objective is to provide an optical transmission device that ensures bandwidth characteristics corresponding to the baud rate of the optical signal. [Means for solving the problem]

[0011] In one embodiment, the optical transmitter includes a conversion device that converts electrical data signals into optical signals, Entered Baud rate of the optical signal Settings The system includes a control unit that changes the peaking adjustment value based on the above, and a driver that changes the bandwidth characteristics of the conversion device based on the adjustment value changed by the control unit. [Effects of the Invention]

[0012] This allows for ensuring bandwidth characteristics corresponding to the baud rate of the optical signal. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1(a) shows an example of an optical transmission system. Figure 1(b) illustrates an example of the bandwidth characteristics of a WDM (Wavelength Division Multiplexing) signal and an optical transmitter. [Figure 2] Figure 2 is a block diagram showing an example of an optical transmission device. [Figure 3]FIG. 3 is a diagram for explaining an example of the band characteristics of the optical transmission device. [Figure 4] FIG. 4(a) is an example of a circuit diagram of the driver. FIG. 4(b) is an example of a circuit diagram of the input buffer and a circuit diagram of the GCA (Gain-Controlled Amplifier). [Figure 5] FIG. 5 is a diagram for explaining an example of the change in the band characteristics of the CDM (Coherent Driver Modulator). [Figure 6] FIG. 6 is a diagram for explaining an example of the noise component superimposed on another adjacent main signal. [Figure 7] FIG. 7 is a flowchart showing an example of the operation of the control unit according to the first embodiment. [Figure 8] FIG. 8(a) is a diagram for explaining an example of the control table. FIG. 8(b) is a diagram for explaining an example of the change in the band characteristics of the optical transmission device. [Figure 9] FIG. 9 is a flowchart showing an example of the operation of the control unit according to the second embodiment. [Figure 10] FIG. 10 is a diagram for explaining an example of the mathematical formula information.

MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, the embodiments for implementing the present case will be described with reference to the drawings.

[0015] (First Embodiment) As shown in FIG. 1(a), the optical transmission system ST includes a plurality of optical transmission devices 10, 20, 30 and a plurality of optical reception devices 70, 80, 90. All of the optical transmission devices 10, 20, 30 are optically connected to an optical multiplexer (specifically, a multiplexer) 40. All of the optical reception devices 70, 80, 90 are optically connected to an optical demultiplexer (specifically, a demultiplexer) 60. The optical multiplexer 40 and the optical demultiplexer 60 are connected via an optical transmission line 50. The optical transmission line 50 includes, for example, an optical fiber.

[0016] Optical transmitters 10, 20, and 30 transmit main signals with different center frequencies. In this embodiment, the main signal is described as an example of an optical signal, but control signals that control the optical transmitters 10, 20, and 30 and the optical receivers 70, 80, and 90 may be used instead of the main signal. For example, optical transmitter 20 transmits a main signal Sf2 with a center frequency f2. Optical transmitters 10 and 30 are basically the same as optical transmitter 20, so a detailed explanation is omitted.

[0017] The optical multiplexer 40 combines the main signals Sf1, Sf2, and Sf3 transmitted from the optical transmitters 10, 20, and 30, respectively, to generate a WDM signal Sfz. The optical multiplexer 40 then transmits the WDM signal Sfz to the optical transmission path 50. When combining the main signals Sf1, Sf2, and Sf3, the optical multiplexer 40 narrows the spacing between adjacent main signals Sf1 and Sf2, and between adjacent main signals Sf2 and Sf3, as shown in Figure 1(b), to generate the WDM signal Sfz. This improves the frequency utilization efficiency.

[0018] The optical demultiplexer 60 receives the WDM signal Sfz that has passed through the optical transmission path 50. The optical demultiplexer 60 demultiplexes the WDM signal Sfz into main signals Sf1, Sf2, and Sf3. The optical demultiplexer 60 transmits, for example, the main signal Sf2 to the optical receiver 80. As a result, the optical receiver 80 receives the main signal Sf2. The optical receivers 70 and 90 are basically the same as the optical receiver 80, so a detailed explanation is omitted.

[0019] Here, as shown in Figure 1(b), the bandwidth characteristic L4 of the optical transmitter 20 is sufficiently maintained relative to the bandwidth characteristic L1 of the main signal Sf2. As a result, the shape of the bandwidth characteristic L1 of the main signal Sf2 is not distorted due to the bandwidth characteristic L4 of the optical transmitter 20. Consequently, a degradation in the signal quality of the main signal Sf2 can be suppressed.

[0020] Incidentally, when the main signal Sf2 is transmitted, the noise component Nz generated by the optical transmitter 20 (hereinafter referred to as the noise component) is also transmitted along with the main signal Sf2. The noise component Nz exists in the region from the lowest frequency to the highest frequency of the bandwidth characteristic L4 of the optical transmitter 20. For this reason, the noise component Nz includes the first adjacent noise component NL, which exists in the region from the lowest frequency of the bandwidth characteristic L4 of the optical transmitter 20 to the lowest frequency of the bandwidth characteristic L1 of the main signal Sf2. Furthermore, the noise component Nz includes the second adjacent noise component NH, which exists in the region from the highest frequency of the bandwidth characteristic L1 to the highest frequency of the bandwidth characteristic L4 of the optical transmitter 20.

[0021] Thus, outside the low-frequency side of the bandwidth characteristic L1 of the main signal Sf2, there is a region where there is no (or very little) component of the main signal Sf2, and only the first adjacent noise component NL exists. In such a case, if another main signal Sf1 is placed adjacent to the main signal Sf2 in this region, the first adjacent noise component NL is superimposed on the main signal Sf1. As a result, the signal quality of the main signal Sf1 deteriorates.

[0022] Similarly, outside the high-frequency side of the bandwidth characteristic L1 of the main signal Sf2, there is a region where there is no (or very little) component of the main signal Sf2, and only the second adjacent noise component NH exists. In such a case, if another main signal Sf3 is placed adjacent to the main signal Sf2 in this region, the second adjacent noise component NH will be superimposed on the main signal Sf3. This degrades the signal quality of the main signal Sf3. As a result, the signal quality of the WDM signal Sfz may decrease, potentially reducing the transmission performance of the optical transmission system ST.

[0023] To suppress such a decrease in transmission performance, it is desirable to make the shape of the bandwidth characteristic L4 of the optical transmitter 20 closer to the shape of the bandwidth characteristic L1 of the main signal Sf2, thereby suppressing the generation of the first adjacent noise component NL and the second adjacent noise component NH. As will be described in detail later, in this embodiment, the shape of the bandwidth characteristic L4 is adaptively adjusted using peaking to bring it closer to the shape of the bandwidth characteristic L1. As a result, even if the shape of the bandwidth characteristic L1 changes according to the baud rate of the main signal Sf2, it is possible to secure a bandwidth characteristic L4 that is close in shape to the shape of the bandwidth characteristic L1.

[0024] Referring to Figure 2, the details of the optical transmitter 20 will be explained. Note that the optical transmitters 10 and 30 have basically the same configuration as the optical transmitter 20, so a detailed explanation will be omitted.

[0025] As shown in Figure 2, the optical transmitter 20 includes a transmitting DSP (Digital Signal Processor, hereinafter referred to as TxDSP) 110 and a DAC (Digital Analogue Converter) 120. The optical transmitter 20 also includes a CDM 130, an ITLA (Integrable Tunable Laser Assembly) 140, and a control unit 150. The CDM 130 is an example of a conversion device. The CDM 130 is an integrated circuit that houses a driver (specifically an optical modulator driver circuit) 131 and a modulator (specifically an optical modulator) 132 in a single package.

[0026] The TxDSP110 receives digital electrical client signals from the client network. These client signals are, for example, Ethernet® signals. The TxDSP110 performs various digital signal processing operations. For example, it converts the client signal into an OTU (Optical Channel Transport Unit) frame, generates an FEC (Forward Error Correction) as an example of an error correction code for the OTU frame, and inserts it into the OTU frame. The TxDSP110 maps the bit data of the OTU frame to symbols by performing digital modulation processing according to the baud rate and modulation scheme (specifically, a multi-level modulation scheme) set by the control unit 150. The TxDSP110 compensates for various losses occurring within the optical transmitter 20 in the OTU frame. For example, the TxDSP110 performs skew compensation and bandwidth characteristic compensation. The TxDSP110 outputs the compensated OTU frame as a data signal to the DAC120.

[0027] The DAC120 converts the data signal from digital to analog and outputs it to the driver 131 of the CDM130. The driver 131 amplifies the data signal. The amplified data signal is used as the drive signal for the modulator 132. Based on the data signal, the modulator 132 modulates the transmitted light (i.e., laser light) input from the ITLA140 and generates a main signal Sf2 having an arbitrary optical waveform. In other words, the modulator 132 converts the data signal into the main signal Sf2. The modulator 132 outputs the main signal Sf2 to the optical multiplexer 40. In this way, the CDM130 converts the data signal into the main signal Sf2 and transmits it.

[0028] The control unit 150 includes a processor and memory, and controls the operation of the TxDSP 110, CDM 130 (specifically the driver 131), and ITLA 140, as shown in Figure 2. The processor includes, for example, a CPU (Central Processing Unit). The memory includes volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory). The control unit 150 may also be an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0029] The control unit 150 performs various settings on the TxDSP 110 and the driver 131 according to the control from the operation terminal 25. The operation terminal 25 may be a PC (Personal Computer) or a smart terminal (e.g., a tablet terminal). As will be described in detail later, for example, when a signal type including baud rate, multi-level modulation scheme, frame format, etc. is input from the operation terminal 25 to the control unit 150, the control unit 150 determines or calculates a peaking adjustment value according to the baud rate and sets the peaking adjustment value in the driver 131.

[0030] The bandwidth characteristics of the optical transmitter 20 will be explained with reference to Figures 3 and 4. The following references may be consulted as needed. (1) Teruo Jyo,et al, “An Over 67-GHz Bandwidth 21-dB Gain 4.5-V ppd Linear Modulator Driver for 100-GBd Coherent Optical Transmitter”, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 31, NO. 6, JUNE 2021 (2)Tie Sun,et al, “Silicon Photonic Mach-Zehnder Modulator Driver for 800+Gb / s Optical Links”, BCICTS,2021

[0031] The bandwidth characteristics (specifically, frequency characteristics or gain characteristics) of the optical transmitter 20 are expressed as a composite bandwidth characteristic of the devices through which data signals pass, among the various devices provided by the optical transmitter 20. In this embodiment, as described above, data signals pass through the DAC120 and CDM130 as devices. On the other hand, data signals do not pass through the ITLA140 as a device. Therefore, as shown in Figure 3, the bandwidth characteristic L4 of the optical transmitter 20 is expressed as a composite bandwidth characteristic of the bandwidth characteristics L2 of the DAC120 and the bandwidth characteristic L3 of the CDM130.

[0032] Here, in order to avoid distorting the shape of the bandwidth characteristic L1 of the main signal Sf2, it is desirable that the shape of the bandwidth characteristic L4 of the optical transmitter 20 be slightly larger than the shape of the bandwidth characteristic L1 of the main signal Sf2, and that the two shapes be similar. As a result, as described above, the noise components present in the region between the bandwidth characteristic L4 of the optical transmitter 20 and the bandwidth characteristic L1 of the main signal Sf2 are reduced, and the degradation of the signal quality of the main signal Sf2 is suppressed.

[0033] Here, the driver 131 of the CDM130 has a characteristic or function called peaking, which amplifies the amplitude component in the bandwidth characteristic L3 of the CDM130 and extends the bandwidth characteristic L3. In this embodiment, such a characteristic or function is called a peaking characteristic. Therefore, as shown in Figure 3, even if the bandwidth characteristic L2 of the DAC120 is insufficient (or lacking) compared to the bandwidth characteristic L1 of the main signal Sf2, the bandwidth characteristic L4 of the optical transmitter 20 can be extended by utilizing the peaking characteristic to extend the bandwidth characteristic L3 of the CDM130.

[0034] As shown in Figure 4(a), the driver 131 includes an input buffer 135 and a GCA 136. The input buffer 135 temporarily stores the data signal output from the DAC 120 via the differential input terminals INP and INN. The GCA 136 acquires the data signal from the input buffer 135, amplifies it, and outputs it to the subsequent circuit. The subsequent circuit includes a preamplifier and an output stage, and outputs the amplified data signal to the modulator 132 via the differential output terminals OUTP and OUTN. The GCA 136 exhibits peaking characteristics. More specifically, as shown in Figure 4(b), the GCA 136 includes a first circuit block 138 for adjusting low-frequency peaking. The GCA 136 also includes a second circuit block 139 for adjusting high-frequency peaking. By adjusting the voltage values ​​applied to the first circuit block 138 and the second circuit block 139 by the control unit 150, the amplitude component can be amplified and the bandwidth characteristic L3 of the CDM 130 can be extended. Furthermore, by adjusting the voltage values ​​applied to the first circuit block 138 and the second circuit block 139 using the control unit 150, the amplitude component can be reduced, thereby shrinking the bandwidth characteristic L3 of the CDM 130.

[0035] Therefore, if the baud rate of the main signal Sf2 and the constant corresponding to the above voltage value (hereinafter referred to as the peaking adjustment value) are pre-associated using a control table or formula, the peaking adjustment value corresponding to the baud rate can be determined or calculated. This identifies the voltage value corresponding to the peaking adjustment value, and the bandwidth characteristic L3 of the CDM130 is expanded or narrowed.

[0036] For example, as shown in Figure 5, the driver 131 can extend the bandwidth characteristic L3-M of the CDM130 corresponding to a medium baud rate to the bandwidth characteristic L3-H of the CDM130 corresponding to a high baud rate. Similarly, the driver 131 can reduce the bandwidth characteristic L3-M of the CDM130 corresponding to a medium baud rate to the bandwidth characteristic L3-L of the CDM130 corresponding to a low baud rate. Therefore, by combining the bandwidth characteristic L2 of the DAC120 and the bandwidth characteristic L3-H of the CDM130, the bandwidth characteristic L4 of the optical transmitter 20 is expanded. Conversely, by combining the bandwidth characteristic L2 of the DAC120 and the bandwidth characteristic L3-L of the CDM130, the bandwidth characteristic L4 of the optical transmitter 20 is reduced.

[0037] Therefore, if the bandwidth characteristic L1 of the main signal Sf2 is a bandwidth characteristic L1-H corresponding to a high baud rate, as shown in Figure 6, then by utilizing the peaking characteristics, the bandwidth characteristic L4 of the optical transmitter 20 will approximate the shape of the bandwidth characteristic L1-H. In other words, the driver 131 should determine the bandwidth characteristic L3-H (see Figure 5) of the CDM 130 so that the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-H.

[0038] On the other hand, even if the bandwidth characteristic L1 of the main signal Sf2 is the bandwidth characteristic L1-L corresponding to a low baud rate, by utilizing the peaking characteristic, the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-L. In other words, the driver 131 only needs to determine the bandwidth characteristics L3-L (see Figure 5) of the CDM 130 so that the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-L.

[0039] As shown in Figure 6, when the bandwidth characteristic L1 of the main signal Sf2 is the bandwidth characteristic L1-L corresponding to a low baud rate, the frequency bandwidth becomes narrower compared to the bandwidth characteristic L1-H. If a bandwidth characteristic L4 that approximates the shape of the bandwidth characteristic L1-H is fixedly set, this bandwidth characteristic L4 becomes excessively wide compared to the bandwidth characteristic L1-L. As a result, a region appears where there is no (or little) component of the main signal Sf2 between this bandwidth characteristic L4 and the bandwidth characteristic L1-L, and only the second adjacent noise component NH exists. In such a case, the signal quality of another main signal Sf3 adjacent to the low baud rate main signal Sf2 may be degraded by the second adjacent noise component NH.

[0040] However, as described above, in this embodiment, even if the bandwidth characteristic L1 of the main signal Sf2 is the bandwidth characteristic L1-L corresponding to a low baud rate, by utilizing the peaking characteristic, the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-L. As a result, a region where only the second adjacent noise component NH exists does not appear, or this region becomes very small. Consequently, in the transmission of WDM signals, the degradation of the signal quality of the main signal Sf3 caused by the second adjacent noise component NH can be suppressed, and a decrease in the transmission performance of the optical transmission system ST can be avoided.

[0041] In this embodiment, the low baud rate can be, for example, 60 Gbaud or 64 Gbaud. The medium baud rate can be, for example, 90 Gbaud or 96 Gbaud. The high baud rate can be, for example, 120 Gbaud or 130 Gbaud.

[0042] Next, the operation of the control unit 150 according to the first embodiment will be described with reference to Figures 7 and 8.

[0043] First, as shown in Figure 7, the control unit 150 receives the signal type input from the operation terminal 25 (step S1). As described above, the signal type includes the baud rate, modulation scheme, frame format, etc., of the main signal Sf2. The control unit 150 accepts the signal type as the setting for the main signal Sf2.

[0044] Upon receiving a signal type, the control unit 150 determines a peaking adjustment value (step S2). As shown in Figure 8(a), the control unit 150 is equipped with a memory 151, which stores a control table 152. The control table 152 defines the correspondence between baud rate and peaking adjustment value. Therefore, when the control unit 150 receives a signal type, it can determine a peaking adjustment value corresponding to the baud rate included in the signal type. In the control table 152, the lower the baud rate, the lower the peaking adjustment value. That is, in the control table 152, smaller baud rates are associated with smaller peaking adjustment values. In addition, although the peaking adjustment value in the first embodiment is shown in hexadecimal, it may be in a format other than hexadecimal.

[0045] Once the peaking adjustment value is determined, the control unit 150 sets the peaking adjustment value to the driver 131 (step S3) and terminates the process. As a result, a voltage value corresponding to the peaking adjustment value is applied to the first circuit block 138 and the second circuit block 139 (see Figure 4(b)), and the bandwidth characteristic L3 of the CDM 130 changes.

[0046] Therefore, for example, if the signal types include high baud rates, the shape of the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-H of the main signal Sf2 with a high baud rate, as shown in Figure 8(b). If the signal types include low baud rates, the shape of the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-L of the main signal Sf2 with a low baud rate, as shown in Figure 8(b). In this way, the optical transmitter 20 according to the first embodiment can ensure a bandwidth characteristic L4 corresponding to the baud rate of the main signal Sf2.

[0047] (Second Embodiment) Next, the operation of the control unit 150 according to the second embodiment will be described with reference to Figures 9 and 10.

[0048] First, as shown in Figure 9, the control unit 150 receives the signal type output from the operation terminal 25 (step S11). The process in step S11 is basically the same as the process in step S1, so a detailed explanation is omitted.

[0049] Upon receiving the signal type, the control unit 150 calculates the peaking adjustment value (step S12). Here, as shown in Figure 10, the control unit 150 holds the setting formula information 153. In other words, the control unit 150 has formula information set in advance. The formula information includes the peaking adjustment value (hexadecimal) = 1B (hexadecimal) × baud rate + D5 (hexadecimal). Constants such as 1B (hexadecimal) and D5 (hexadecimal) can be appropriately determined according to the design, experiment, etc.

[0050] Thus, the control unit 150 defines the correspondence between the baud rate and the peaking adjustment value. Therefore, when the control unit 150 receives a signal type, it can calculate the peaking adjustment value corresponding to the baud rate included in the signal type. In this formula information, the lower the baud rate, the lower the peaking adjustment value. That is, in this formula information, a smaller baud rate results in a smaller peaking adjustment value. Also, although the peaking adjustment value in the second embodiment is shown in hexadecimal, it may be in a format other than hexadecimal.

[0051] Once the peaking adjustment value is calculated, the control unit 150 sets the peaking adjustment value to the driver 131 (step S13) and terminates the process. As a result, a voltage value corresponding to the peaking adjustment value is applied to the first circuit block 138 and the second circuit block 139 (see Figure 4(b)), and the bandwidth characteristic L3 of the CDM 130 changes.

[0052] Therefore, for example, if the signal types include high baud rates, the shape of the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-H of the main signal Sf2 with a high baud rate. If the signal types include low baud rates, the shape of the bandwidth characteristic L4 of the optical transmitter 20 approximates the shape of the bandwidth characteristic L1-L of the main signal Sf2 with a low baud rate. In this way, even with the optical transmitter 20 according to the second embodiment, it is possible to secure a bandwidth characteristic L4 corresponding to the baud rate of the main signal Sf2.

[0053] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims.

[0054] Furthermore, the following additional information is disclosed regarding the above explanation. (Note 1) An optical transmission device comprising: a conversion device that converts an electrical data signal into an optical signal; a control unit that changes a peaking adjustment value based on the baud rate of the optical signal; and a driver that changes the bandwidth characteristics of the conversion device based on the adjustment value changed by the control unit. (Note 2) The optical transmitting device according to Note 1, characterized in that the peaking is a characteristic that amplifies the amplitude component in the bandwidth characteristics of the conversion device. (Note 3) The optical transmission device according to Note 1 or 2, characterized in that the driver changes the bandwidth characteristics of the conversion device by adjusting the peaking based on the adjustment value. (Note 4) The optical transmission apparatus according to Note 1 or 2, characterized in that the control unit includes a memory for storing a table that defines the correspondence between the baud rate and the adjustment value, and determines the adjustment value according to the baud rate based on the table. (Note 5) The optical transmitting device according to Note 4, characterized in that the correspondence is such that the adjustment value decreases in accordance with the decrease in the baud rate. (Note 6) The optical transmission apparatus according to Note 1 or 2, characterized in that the control unit holds mathematical formula information that defines the correspondence between the baud rate and the adjustment value, and calculates the adjustment value according to the baud rate based on the mathematical formula information. (Note 7) The optical transmitting device according to Note 6, characterized in that the correspondence is such that the adjustment value decreases in accordance with the decrease in the baud rate. [Explanation of symbols]

[0055] ST Optical Transmission Systems 10,20,30 Optical Transmitter 110 TxDSP 120 DAC 130 CDM 131 Driver 132 Modulator 136 GCA 138 First Circuit Block 139 Second Circuit Block 140 ITLA 150 Control Unit 151 memory 152 Control Table 153 Setting Formula Information

Claims

1. A conversion device that converts electrical data signals into optical signals, A control unit that changes the peaking adjustment value based on the baud rate setting of the input optical signal, A driver that changes the bandwidth characteristics of the conversion device based on the adjustment value changed by the control unit, An optical transmitting device equipped with the following features.

2. The aforementioned peaking is a characteristic that amplifies the amplitude component in the bandwidth characteristics of the conversion device. The optical transmitting device according to feature 1.

3. The driver changes the bandwidth characteristics of the conversion device by adjusting the peaking based on the adjustment value. The optical transmitting device according to claim 1 or 2.

4. The control unit includes a memory that stores a table defining the correspondence between the baud rate and the adjustment value, and determines the adjustment value according to the baud rate based on the table. The optical transmitting device according to claim 1 or 2.

5. The aforementioned correspondence is such that the adjustment value decreases in proportion to the decrease in the baud rate. The optical transmitting device according to feature 4.

6. The control unit holds mathematical formula information that defines the correspondence between the baud rate and the adjustment value, and calculates the adjustment value according to the baud rate based on the mathematical formula information. The optical transmitting device according to claim 1 or 2.

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