JP5669665B2 - Optical transceiver - Google Patents

Description

  The present invention relates to an optical transceiver used for high-speed optical transmission / reception in an optical access network.

  With the spread of the Internet, service diversification has progressed, and the required transmission rate required for optical access networks in recent years is increasing year by year. At present, in Japan, optical communication with a maximum transmission rate of 1 Gbps is widely provided, but research has been made to further increase the transmission rate.

  In recent years, as shown in Non-patent Document 1, 10 Gbps high-speed optical transmission / reception has been standardized, and a (A) PD-TIA (Photo Diode with Trans-Impedance Amplifier) optical module is applied to the receiving unit. An EML (electroabsorption modulator monolithically integrated laser diode) optical module in which a DFB-LD (Distributed Feed-Back Laser Diode) and an electroabsorption (EA) optical modulator are integrated is applied to the 10 Gbps transmitter. The Research on ultra high-speed optical access systems exceeding 10 Gbps is also underway.

  In order to realize low power consumption and low device installation cost, there is a constant demand for miniaturization and high density devices in access network optical transceivers. Therefore, the 10 Gbps transmission module and the reception module as described above are integrated and supplied as a single-core bidirectional optical module. In the optical transceiver board, the transmission function and the reception function are generally mounted on a single board.

  In such an optical transmitter / receiver in which an optical transmission unit and an optical reception unit are integrated, there is a possibility that an electric signal of the transmission unit may cause crosstalk that affects the reception signal via the substrate / space / module. . In electrical crosstalk, the amount of crosstalk increases as the frequency increases, and the direction and size of the generated crosstalk change depending on the surrounding structure, making improvement and analysis difficult.

  As one method for avoiding these crosstalks, it is effective to increase the distance between transmission and reception. However, in a single-core bi-directional optical module, it is difficult to design a distance between transmission and reception in order to maintain the coupling of light. Taking a method is not appropriate.

  Another method for suppressing crosstalk is to suppress spatially propagated electrical crosstalk by using complementary signals such as a differential signal transmission method. In such a differential signal transmission system, the occurrence of electrical crosstalk can be suppressed on the transmission side, and the effect of electrical crosstalk is also suppressed on the reception side. In Non-Patent Document 2, since the crosstalk characteristic is degraded by a single-phase transmission line, crosstalk can be suppressed by differentially driving both the transmission LD and the reception APD-TIA. Has been shown experimentally.

  On the other hand, an EA optical modulator is composed of a semiconductor element that absorbs light by applying an electric field, and is used as a modulator for high-speed optical communication because it has a low chirp and a high response speed. Non-Patent Document 3 shows an example in which an EML optical module is used as a 10 Gbps 40 km transmission optical module.

  Here, FIG. 8 is a block diagram showing a conventional transceiver (connection configuration example of an EML optical module and a drive circuit board). In FIG. 8, the CAN-type EML optical module 2 is connected to the drive circuit board 4 via the flexible printed board 3. The EML optical module 2 includes a monitor PD 11, an LD 12, an EA 13, a matching resistor 14, a thermistor 15, a Peltier element 16, and a capacitor 17. The drive circuit board 4 includes a driver IC 31 for driving the LD 12 and the EA 13, a TEC (Thermoelectric Cooler) control unit 32 for controlling the LD temperature, AC coupling capacitors 33a and 33b, and a bias line for applying an EA bias. 35 and a termination resistor 34 for a reverse-phase signal are provided.

  Here, the LD 12 and the EA 13 shown in FIG. 8 are often applied as an integrated element (EML) element common to the cathode. Also, unlike the connection method shown in FIG. 8, a connection method in which the common cathode of EA13 and LD12 is floated in a DC manner from the ground, or DC coupling that is not AC-coupled to the driver IC 31 is used on the cathode side of EA13. The However, single-phase driving using only a single-phase signal of the driver IC as an applied signal to the EA is a common usage of the EA modulator.

  However, on the other hand, a differential driving method for the EA modulator has also been proposed. For example, in Patent Document 1, a good extinction characteristic is obtained even when the driving force of the driver is low by driving the EA modulator differentially. A method has been proposed.

JP 2002-277840 A

IEEE802.3av 10G-EPON Task Force, [online], [Search April 19, 2011], Internet (URL: http://www.ieee802.org/3/av/index.html) Yoshida T et al., “First single-fibre bi-directional XFP transceiver for optical metro / access networks,” 31th ECOC2005, Sept. 25-29, 2005, Glasgow, Scotland, UK, Tech. Dig. We4. P.021 . Anzai et al., “Compact 10Gbit / s optical transceiver for 40km transmission with low power consumption,” 2010 IEICE General Conference, B-10-75

  As described above, crosstalk can be suppressed by differentially driving the transmission unit and reception unit of the optical transceiver. However, when the above-described conventional general EML module connection configuration is applied to an access optical transceiver, the opposite phase side of the signal for driving the EML is terminated at the drive circuit board, and the flexible board It becomes a single-phase line from to the optical module. For this reason, there arises a problem that crosstalk due to the transmission signal occurs and the reception sensitivity characteristic of the receiver deteriorates.

  Further, when the differential method of the EA modulator described in Patent Document 1 is applied to an EML element in which the cathodes of the EA and the LD are shared and integrated, the light output from the LD light source fluctuates. Therefore, a stable light output cannot be obtained and application is difficult.

  The present invention has been made to solve the above-described problems, and suppresses electric field radiation from a flexible printed circuit board that connects a drive circuit board and an optical module, thereby realizing low crosstalk characteristics. It is an object to obtain an optical transceiver that can be used.

An optical transmitter / receiver according to the present invention includes an optical transmitter having a semiconductor laser device that converts electricity into light, an optical modulator that modulates light of the semiconductor laser device, and a semiconductor optical device that converts an optical signal into an electrical signal. A single-core bidirectional optical module integrated with an optical receiving unit, an optical transceiver board having a differential driver circuit for driving the optical module, and a flexible connection between the optical module and the driving circuit board and a printed circuit board, the optical module, wherein each of the flexible printed circuit board and the drive circuit board, have a main electrical signal transmission line pair comprising a positive phase signal transmission path and a transmission path for the reverse phase signal The modulation unit is an electroabsorption optical modulator that modulates using only a positive phase signal, and the optical module includes the termination of the reverse phase signal transmission path and the electric field. Equivalent circuit components constituting the equivalent circuit of Osamugata light modulator is provided.

  According to the optical transceiver of the present invention, each of the optical module, the flexible printed circuit board, and the optical transceiver board has a pair of main electric signal transmission paths each including a normal phase signal transmission path and a negative phase signal transmission path. Therefore, it is possible to suppress electric field radiation from the flexible printed circuit board connecting the drive circuit board and the optical module, and to realize low crosstalk characteristics.

It is a block diagram which shows the optical transmitter-receiver by Embodiment 1 of this invention. It is a graph which shows the optical output characteristic with respect to the applied bias of an EA optical modulator. It is a block diagram which shows the optical transmitter-receiver by Embodiment 2 of this invention. It is a graph which shows the relationship of the bias current value with respect to the optical input power to an EA element at the time of applying a certain arbitrary reverse bias to an EA element. It is a block diagram which shows the optical transmitter / receiver by Embodiment 3 of this invention. It is a block diagram which shows the optical transmitter-receiver by Embodiment 4 of this invention. It is a block diagram which shows the optical transmitter-receiver by Embodiment 5 of this invention. It is a block diagram which shows the conventional optical transmitter / receiver.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
1 is a configuration diagram showing an optical transceiver (an example of a connection configuration between an EML optical module of a low crosstalk optical transceiver and a drive circuit board) according to Embodiment 1 of the present invention.
In FIG. 1, an optical transceiver (low crosstalk optical transceiver) 1 includes a CAN-type EML optical module 2, a flexible printed circuit board 3, and a drive circuit board 4. The CAN-type EML optical module 2 and the drive circuit board 4 are connected to each other via a flexible printed board 3.

  The EML optical module 2 includes a monitor photodiode (hereinafter referred to as monitor PD) 11, a laser diode (hereinafter referred to as LD) 12 as a semiconductor laser device, and an electroabsorption optical modulator (hereinafter referred to as EA optical modulator) 13a. And an electroabsorption semiconductor element (hereinafter referred to as EA element) 13b having the same capacity as the EA modulator 13a, termination resistors 14a and 14b, thermistor 15, Peltier element 16 and capacitors 17a and 17b. Yes. Here, the EML optical module 2 includes an optical transmitter that includes the LD 12 and the EA optical modulator 13a, and an optical receiver that includes a semiconductor optical device that converts the optical signal into an electrical signal and a demodulator (both not shown). Is a single-core bidirectional optical module.

  The monitor PD 11 generates a current depending on the intensity of the laser beam in order to monitor the laser output power. The terminating resistor 14a is a terminating resistor for signals applied to the EA optical modulator 13a. The termination resistor 14b is a termination resistor for a signal applied to the EA element 13b. The resistance value of the thermistor 15 changes according to the temperatures of the LD 12 and the EA optical modulator 13a. The Peltier element 16 is for controlling the temperature of the LD 12 and the EA light modulator 13a.

  A circuit for driving the EA light modulator 13 a and the LD 12 is mounted on the drive circuit board 4. Specifically, the drive circuit board 4 is provided with a driver IC (differential driver circuit) 31, a TEC control unit 32, capacitors 33a and 33b, and bias lines 35a and 35b. Capacitors 33a and 33b are for AC coupling the positive and negative phase outputs of the driver IC31. The bias lines 35a and 35b are for applying a DC bias to the EA optical modulator 13a and the EA element 13b. In FIG. 1, white circles between the EML optical module 2 and the flexible printed circuit board 3 and between the flexible printed circuit board 3 and the drive circuit board 4 mean connection points of the respective components.

  Next, operations of the EML optical module 2 and the drive circuit board 4 in the first embodiment will be described. In order to operate the EML optical module 2 of FIG. 1, the temperature of the LD 12, the EA optical modulator 13 a and the EA element 13 b is kept constant, and the automatic output power control function (APC function) that the LD 12 keeps outputting at a constant power. It is necessary to realize three functions on the drive circuit board 4 side: an automatic temperature control function (ATC function) for controlling, and a modulation function (modulation function) for applying a signal bias to the EA optical modulator 13a. In the configuration of the first embodiment, the APC function and the modulation function are realized by the driver IC 31, and the ATC function is realized by the TEC control unit 32.

  Here, when an external optical modulator such as the EA optical modulator 13a is used, a stable and constant output power must be obtained from the LD 12. However, even if the LD continues to pass a constant current, the output power fluctuates due to factors such as aging. For this reason, feedback control using the monitor PD11 is performed. The light output from the LD 12 is received by the monitor PD 11 and converted from light to current using the characteristic of flowing current according to the input light power of the PD, which is a light receiving element.

  The current of the monitor PD11 is fed back to the driver IC 31. A reference current value is set in advance in the driver IC 31, and the amount of current applied to the LD 12 is controlled so that the fed back PD current is always equal to the reference current value. In addition, since the current from the monitor PD 11 depends on the optical output power of the LD 12, for example, when the optical output power of the LD 12 deteriorates due to deterioration over time, the current supplied by the monitor PD 11 also decreases. Therefore, the APC function of the driver IC 31 controls to increase the value of the current applied to the LD 12, increase the optical output power, and restore the current from the monitor PD 11.

  In addition, the absorption light wavelength of the EA optical modulator 13a and the optical output power and wavelength of the LD 12 have temperature dependence. Therefore, the thermistor 15 and the Peltier element 16 are used in the EML optical module 2 for temperature control. Since the thermistor 15 detects the temperatures of the LD 12 and the EA light modulator 13a, the thermistor 15 has resistance values corresponding to the temperatures of the LD 12 and the EA light modulator 13a. The TEC control unit 32 detects the internal temperature of the EML optical module 2 based on the voltage or current applied to the thermistor 15, and changes the amount and direction of the current flowing to the Peltier element 16 to change the LD 12 and the EA optical modulator 13a. To control the temperature.

  Subsequently, a modulation signal applied to the EA optical modulator 13a will be described. FIG. 2 is a graph showing optical output characteristics with respect to an applied bias of the EA optical modulator. In FIG. 2, the horizontal axis represents the bias applied to the EA anode, and the vertical axis represents the optical output power. The characteristic of the EA light modulator 13a is a characteristic that absorbs and extinguishes light as the deep bias is applied. As shown in (1) of FIG. 2, by applying an electric waveform distorted around the center bias, As shown in (2) of FIG. 2, an optical output waveform without distortion can be obtained.

  Returning to FIG. 1, the output waveform from the driver IC 31 is applied to the EA optical modulator 13a using an AC coupling configuration in which only the AC component is extracted by the capacitor 33a and the center bias is determined using the bias line 35a. To generate a signal. On the EML optical module 2 side, a series connection body of an impedance matching termination resistor 14a and a capacitor 17a is connected in parallel with the EA optical modulator 13a, and a signal is applied to the EA optical modulator 13a without reflection.

  The transmitted optical output power and optical waveform are determined by the continuous light from the LD 12 and the electrical signal applied to the EA optical modulator 13a. The capacitor 17a connected in series with the termination resistor 14a is used to suppress an increase in DC current from the termination resistor 14a by separating the bias line and the ground in a DC manner.

  Here, the signal on the output transmission line of the driver IC 31 to the EA optical modulator 13a and the terminating resistor 14a is a positive phase signal, and the signal on the non-applied side is a negative phase signal. The negative-phase signal line is provided with a capacitor 33b having the same AC coupling capacity as the positive-phase signal line, a bias line 35b, an EA element 13b having the same element capacity as the EA optical modulator 13a, a termination resistor 14b, and a capacitor 17b. As described above, each of the EML optical module 2, the flexible printed circuit board 3, and the drive circuit board 4 has a pair of main electric signal transmission lines including a normal phase signal transmission line and a negative phase signal transmission line. Yes.

  The signal applied to the EA element 13b and the termination resistor 14b is a signal obtained by shifting the phase of the positive phase signal by 180 degrees. As described above, the optical output to be transmitted is determined by the LD 12 and the EA optical modulator 13a, and the light coupling requirement of the LD 12 and the EA element 13b is not strict. The EA element 13b only needs to modulate the leakage light from the LD 12, and the modulated light from the EA element 13b is not output. Therefore, the light modulated by the EA element 13b does not affect the light output from the EA light modulator 13a at all, and therefore no characteristic deterioration from the prior art due to the configuration of the first embodiment occurs. .

  Next, the effect of Embodiment 1 is demonstrated. By adopting the configuration of the first embodiment as described above, a positive phase signal transmission line and a negative phase signal transmission line are formed on the flexible printed circuit board 3 that connects the EML optical module 2 and the drive circuit board 4. These positive-phase and negative-phase signal transmission lines pass signals of opposite phases, and electric fields of opposite phases are generated. As a result, electric fields of opposite phases are generated so as to cancel each other's electric fields, so that signals radiated to the space (field emission) are suppressed, and crosstalk to the receiver and other transmitters is improved. be able to. That is, low crosstalk characteristics can be realized.

  Further, in the first embodiment, equal length wiring from the driver IC 31 to the termination resistor 14a and the capacitor 17a and from the driver IC 31 to the termination resistor 14b and the capacitor 17b is possible, and the EA optical modulator 13a and the EA element 13b By making the respective element capacities equal, it is possible to make the normal-phase and reverse-phase transmission lines viewed from the driver IC 31 appear to be very equal loads, and the high-frequency characteristics can be improved.

Embodiment 2. FIG.
In the first embodiment, the EML optical module is configured to increase the number of terminals for reverse phase signal and terminate the reverse phase signal in the EML optical module. On the other hand, Embodiment 2 shows an embodiment in which the terminals that can be used in the EML optical module have the same number of restrictions as in the conventional example as shown in FIG.

  3 is a block diagram showing an optical transceiver according to Embodiment 2 of the present invention. Descriptions of elements and functions similar to those in FIG. 1 are omitted. Here, in the configuration shown in FIG. 3 of the second embodiment, unlike the configuration of the first embodiment shown in FIG. 1, the monitor PD 11 for monitoring the optical output of the LD 12 from the EML optical module 2 is omitted, and the driving circuit board is omitted. In this configuration, a resistance (current detection means) 36 for detecting a DC voltage or current is provided in the four negative-phase signal bias lines 35b. Other configurations are the same as those in the first embodiment.

  Next, the operation of the optical transceiver according to the second embodiment will be described. In order to operate the EML optical module 2 shown in FIG. 3, an automatic output power control function (APC function) in which the LD 12 continues to output at a constant power, the LD 12 and the EA optical modulator 13a, as in the first embodiment, It is necessary to use an automatic temperature control function (ATC function) that controls the temperature of the EA element 13b to be constant and a modulation function (modulation function) that applies a signal bias to the EA optical modulator 13a. Among these, the ATC function and the modulation function are the same as those in the first embodiment, and the description thereof is omitted.

  The LD monitor function of the automatic output power control function (APC function) of the second embodiment is realized by the EA element 13b, which is one of the termination loads of the reverse phase signal, and the resistor 36 inserted in the bias line 35b. The EA light modulator 13a and the EA element 13b have a characteristic of absorbing light and converting it into a current. The amount of light absorption current depends on the magnitude of the input optical power when the same bias is applied.

  FIG. 4 is a graph showing the relationship of the bias current value with respect to the optical input power to the EA element 13b when an arbitrary reverse bias is applied to the EA element 13b. As shown in FIG. 4, since the EA element 13b flows a light absorption current depending on the optical input power, in order to monitor the optical output of the LD 12, it is only necessary to monitor the bias current value or something in place thereof. .

  Returning to FIG. 3, the driver IC 31 monitors the voltage value on the inductor side of the resistor 36 inserted in the bias line 35b, and outputs the LD 12 so that the voltage value is the same as the initial setting value (for example, the center bias). To control. For example, when the voltage value on the inductor side of the resistor 36 is a shallow bias, the driver IC 31 that has detected that the light absorption current of the EA element 13b has increased increases the optical output power so that no bias current flows through the LD 12. Control in the direction to suppress. On the other hand, when the voltage value on the inductor side of the resistor 36 becomes a deep bias, the optical output power is controlled to increase so that a bias current flows more through the LD 12.

  Next, the effect of Embodiment 2 is demonstrated. In the second embodiment, as in the first embodiment, the positive phase signal transmission line and the negative phase signal transmission line are provided on the flexible printed circuit board 3 that connects the EML optical module 2 and the drive circuit board 4. It is possible to generate cross-phase electric fields in the phase and reverse-phase signal transmission lines, respectively, and to improve crosstalk with respect to the receiver and other transmitters.

  In addition, since the driver IC 31 and the terminal can be equally arranged and wired with the same length, there is an effect of improving the high frequency characteristics. Furthermore, by using the reverse-phase signal transmission line in combination with the power monitor function as compared with the first embodiment, the number of output terminals of the EML optical module 2 can be realized with the configuration of the conventional technique. Furthermore, the element of the monitor PD 11 can be completely removed from the configuration of the first embodiment, and can be realized without increasing the number of output terminals from the EML optical module 2 from the configuration of the prior art.

Embodiment 3 FIG.
FIG. 5 is a configuration diagram illustrating an optical transceiver according to the third embodiment. In the following, description of elements similar to those of the first and second embodiments shown in FIGS. In the third embodiment, unlike the second embodiment, the monitor PD is used as the end of the reverse-phase signal transmission line of the driver IC 31. That is, the configuration of the third embodiment is different from the configuration of the second embodiment in that a monitor PD 11 is used instead of the EA element 13b having the configuration of the second embodiment shown in FIG.

  Next, the operation of the optical transceiver according to the third embodiment will be described. In order to operate the EML optical module 2 of FIG. 5, as in the first embodiment, the automatic output power control function (APC) in which the LD 12 keeps outputting at a constant power, and the temperatures of the LD 12 and the EA optical modulator 13a. It is necessary to use three functions: an automatic temperature control function (ATC) for controlling the temperature constant, and a modulation function for applying a modulation signal to the EA optical modulator 13a. Among these, the automatic temperature control function (ATC) and the modulation function are the same as those in the second embodiment, and a description thereof will be omitted.

  The automatic output power control function (APC) of the third embodiment will be described. The monitor PD 11 according to the third embodiment is mounted as an end of a reverse phase signal, converts continuous light from the LD 12 into a current, and supplies the DC component to the bias line 35b. Therefore, in order to monitor the optical output of the LD 12, the bias current value may be monitored by some method. Therefore, the driver IC 31 of the third embodiment monitors the voltage value on the inductor side of the resistor 36 inserted in the bias line 35b, and controls the output of the LD 12 so that the voltage value becomes the same as the initial setting value.

  For example, when the voltage value on the inductor side of the resistor 36 becomes a shallow bias, the driver IC 31 detects that the light absorption current of the EA element 13b has increased, and controls the bias current not to flow through the LD 12. . On the other hand, when the voltage value on the inductor side of the resistor 36 becomes a deep bias, the driver IC 31 controls the bias current to flow through the LD 12 more. The initial value of the voltage value on the inductor side of the resistor 36 needs to be set to a voltage value at which the monitor PD 11 operates sufficiently.

  Next, effects of the third embodiment will be described. In the third embodiment, as in the first embodiment, a positive phase signal transmission line and a negative phase signal transmission line are provided on the flexible printed circuit board 3 that connects the EML optical module 2 and the drive circuit board 4. With this configuration, it is possible to generate cross-phase electric fields in the normal-phase and reverse-phase signal transmission lines and improve crosstalk with respect to the reception unit and other transmission units.

  In addition, since it is possible to arrange the driver IC 31 and the terminal to be equally arranged and have the same length wiring, there is an effect of improving the high frequency characteristics. Furthermore, as compared with the first embodiment, the number of output terminals of the EML optical module 2 can be realized with the configuration of the prior art by using the reverse phase signal transmission line in combination with the power monitor function. Further, crosstalk can be suppressed without applying an EA element which is an expensive optical element as compared with the second embodiment.

Embodiment 4 FIG.
FIG. 6 is a block diagram showing a transceiver according to Embodiment 4 of the present invention. In FIG. 6, description of elements similar to those in FIGS. In the fourth embodiment, a capacitor (equivalent circuit constituent element) 18 having a capacity equivalent to the element capacity of the EA optical modulator 13a is used instead of the EA element 13b arranged at the end of the antiphase signal in the first embodiment. The capacitor 18 is connected in parallel with the termination resistor 14b. That is, the configuration of the fourth embodiment is different from the configuration of the first embodiment in that a capacitor 18 is used instead of the EA element 13b having the configuration of the first embodiment shown in FIG. Other configurations are the same as those in the first embodiment.

  Next, effects of the fourth embodiment will be described. In the fourth embodiment, as in the first embodiment, the flexible printed circuit board 3 that connects the EML optical module 2 and the drive circuit board 4 is provided with the positive phase signal transmission line and the negative phase signal transmission line. It is possible to improve the crosstalk with respect to the receiving unit and other transmitting units by generating electric fields with opposite phases in the normal phase and reverse phase signal transmission lines. In addition, since the driver IC 31 and the terminal can be equally arranged and wired with the same length, there is an effect of improving the high frequency characteristics. Furthermore, compared with the configuration of the first embodiment, a sufficient effect for suppressing crosstalk can be desired without increasing the number of EA elements that are expensive optical elements.

Embodiment 5 FIG.
FIG. 7 is a block diagram showing an optical transceiver according to Embodiment 5 of the present invention. A description of the same elements and the same functions as those in the above embodiments is omitted. In FIG. 7, in the fifth embodiment, instead of the EA element 13b arranged at the end of the antiphase signal in the first embodiment, a capacitor (equivalent to an element capacity of the EA optical modulator 13a) is substituted. Circuit component) 23 is used. However, in the optical transceiver of the fifth embodiment, the capacitor 23, the termination resistor 21, and the capacitor 22, which are termination loads for the reverse phase signal, are arranged outside the EML optical module 2 and mounted on the flexible printed circuit board 3. It has a configuration characterized by.

  Here, in order to arrange the transmission paths of the normal phase signal and the reverse phase signal in parallel as much as possible and suppress crosstalk, it is necessary to bring the end of these transmission paths close to the EML optical module 2. Therefore, the EML optical module 2 according to the fifth embodiment is assumed to have a CAN configuration, and the capacitor 23, the termination resistor 21 and the capacitor 22 which are termination loads for the reverse phase signal are the EML optical module 2 and the flexible printed board 3. It is the structure mounted in the CAN back surface used as a contact. Other configurations are the same as those in the first embodiment.

  Next, effects of the fifth embodiment will be described. In the fifth embodiment, similarly to the previous embodiments, the flexible printed circuit board 3 that connects the EML optical module 2 and the drive circuit board 4 is provided with a normal phase signal transmission line and a negative phase signal transmission line. In addition, it is possible to improve the crosstalk for the receiving unit and other transmitting units by generating electric fields of opposite phases in the normal phase and reverse phase signal transmission lines. Further, since the configuration of the EML optical module 2 is exactly the same as the configuration of the EML optical module 2 of the conventional optical transceiver shown in FIG. 8, it is the simplest of crosstalk among the embodiments described so far. Suppression can be realized.

  DESCRIPTION OF SYMBOLS 1 Optical transmitter / receiver, 2 EML optical module, 3 Flexible printed circuit board, 4 Drive circuit board, 11 PD (photodiode), 12 LD (semiconductor laser device), 13a EA light modulator (electroabsorption type optical modulator), 13b EA element (electroabsorption semiconductor element), 14a, 14b termination resistor, 15 thermistor, 16 Peltier element, 17 capacitor, 17a, 17b capacitor, 18 capacitor (equivalent circuit constituent element), 21 termination resistor, 22 capacitor, 23 capacitor ( Equivalent circuit component), 31 driver IC (differential driver circuit), 32 TEC control unit, 33a, 33b capacitor, 34 termination resistor, 35a, 35b bias line, 36 resistance (current detection means).

Claims (2)

An optical transmitter having a semiconductor laser device for converting electricity into light and an optical modulator for modulating the light of the semiconductor laser device, and an optical receiver having a semiconductor optical device and a demodulator for converting an optical signal into an electric signal An integrated single-core bidirectional optical module;
An optical transceiver board having a differential driver circuit for driving the optical module;
A flexible printed circuit board connecting the optical module and the drive circuit board;
Said optical module, wherein each of the flexible printed circuit board and the drive circuit board, have a main electrical signal transmission line pair comprising a positive phase signal transmission path and a transmission path for the reverse phase signal,
The modulation unit is an electroabsorption optical modulator that modulates using only a positive phase signal,
2. An optical transceiver according to claim 1, wherein the optical module is provided with an equivalent circuit constituting element that terminates the reverse-phase signal transmission line and forms an equivalent circuit of the electroabsorption optical modulator . An optical transmitter having a semiconductor laser device for converting electricity into light and an optical modulator for modulating the light of the semiconductor laser device, and an optical receiver having a semiconductor optical device and a demodulator for converting an optical signal into an electric signal An integrated single-core bidirectional optical module;
An optical transceiver board having a differential driver circuit for driving the optical module;
A flexible printed circuit board connecting the optical module and the drive circuit board;
Said optical module, wherein each of the flexible printed circuit board and the drive circuit board, have a main electrical signal transmission line pair comprising a positive phase signal transmission path and a transmission path for the reverse phase signal,
The modulation unit is an electroabsorption optical modulator that modulates using only a positive phase signal,
The connection point between the optical module and the flexible printed circuit board is provided with an equivalent circuit component that forms an equivalent circuit of the electroabsorption optical modulator that terminates a reverse-phase signal transmission line. An optical transceiver.

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