Light receiving unit

Abstract

The invention relates to the technical field of optical communication, in particular to an optical receiving unit which is used for reducing DCD in an optical signal path of the optical receiving unit and can guarantee the receiving performance of the optical receiving unit. The optical receiver unit comprises a comparator and a controlled variable current source. Wherein the comparator is used for receiving a second voltage signal output by the automatic gain controller and receiving a reference voltage signal determined according to a target voltage signal output by the transimpedance amplification unit; and outputting a first control signal according to the second voltage signal and the reference voltage signal. The controlled variable current source is used for receiving the first control signal; and reducing a differential voltage signal output by a differential amplification unit according to the first control signal.

Description

Technical Field

[0001] This application relates to the field of optical communication technologies, and in particular, to an optical receiving unit. Background Art

[0002] In optical communication networks such as passive optical networks (PONs), optical receivers based on trans-impedance amplifiers (TIAs) are generally used as optical receivers of optical network devices such as optical network units (ONUs).

[0003] In an optical receiver, an incident optical signal can be converted into a current signal by a photodiode (PD). Due to certain offset characteristics of the PD, the converted current signal also includes an unwanted offset current signal. In addition, the converted current signal is generally converted into a voltage signal by a trans-impedance amplifier (TIA). And the TIA also includes an additional inherent voltage signal. Thus, due to the existence of the offset current signal and the additional inherent voltage signal, a large duty cycle distortion (DCD) is caused. Summary of the Invention

[0004] Embodiments of this application provide an optical receiving unit, which can reduce DCD in the optical receiving unit through a comparator and a controlled variable current source, thereby improving the receiving performance of the optical receiving unit.

[0005] In a first aspect, an optical receiving unit is provided. The optical receiving unit may at least include: a photodetection unit, a trans-impedance amplification unit, an automatic gain controller, a differential amplification unit, a first comparator, and a controlled variable current source. Among them, the photodetection unit is configured to convert a received optical signal into a current signal; the trans-impedance amplification unit is configured to convert the current signal into a first voltage signal; the differential amplification unit is configured to convert the first voltage signal into a first differential voltage signal. The first comparator is configured to receive a second voltage signal output by the automatic gain controller and receive a first reference voltage signal; and output a first control signal according to the second voltage signal and the first reference voltage signal; where the first reference voltage is determined according to a target voltage signal output by the trans-impedance amplification unit. The controlled variable current source is configured to receive the first control signal; and adjust the first differential voltage signal to a second differential voltage signal according to the first control signal; where an absolute value of the second differential voltage signal is less than an absolute value of the first differential voltage signal.

[0006] In the optical receiving unit, the first comparator can be used to determine whether there is an offset current signal in the optical receiving unit. When it is detected that there is an offset current signal, the controlled variable current source can be controlled to start working. When the controlled variable current source is working, the differential voltage signal output by the differential method unit can be reduced, thereby reducing the DCD in the optical receiving unit and improving the receiving performance of the optical receiving unit.

[0007] In a possible design, the optical receiving unit further includes: a second comparator. The second comparator is configured to receive the second voltage signal output by the automatic gain controller and receive a second reference voltage signal; and output a second control signal according to the second voltage signal and the second reference voltage signal; wherein, the second reference voltage signal is determined according to the target voltage signal of the automatic gain controller; a first difference between the first reference voltage signal and the target voltage signal is different from a second difference between the second reference voltage signal and the target voltage signal. The controlled variable current source is configured to receive the second control signal; and adjust the first differential voltage signal to a third differential voltage signal according to the second control signal; wherein, an absolute value of the third differential voltage signal is less than an absolute value of the first differential voltage signal.

[0008] In this design, the optical receiving unit can also achieve higher-resolution control through multiple comparators. By setting different values for the reference voltages input to each comparator, as the offset current signal and the voltage signal output by the automatic gain controller increase, an incremental change of the controlled variable current source can be achieved, and accordingly, a corresponding reduction of the DCD can be achieved. In this way, a larger range of offset current signals and voltage signals output by the automatic gain controller can be satisfied.

[0009] In another possible design, the optical receiving unit further includes: a controlled variable voltage source or a controlled variable resistor. Wherein, the controlled variable voltage source or the controlled variable resistor is configured to receive the first control signal; and adjust the power supply voltage signal of the differential amplification unit according to the first control signal to obtain a first input voltage signal; wherein, the first input voltage signal serves as the target power supply voltage signal of the differential amplification unit.

[0010] In this design, the first comparator can not only control the operation of the controlled variable current source, but also control the operation of the controlled variable voltage source or the controlled variable resistor. Thus, by adjusting the operation of the controlled variable voltage source or the controlled variable resistor, the voltage range of the differential amplification unit can be adjusted. Furthermore, in the scenario where the normal operation of the differential amplification unit is ensured, the adjustable range of the controlled variable current source can be increased. It can also be understood that this can avoid the abnormal operation of the differential amplification unit caused by excessive adjustment of the differential amplification signal by the controlled variable current source.

[0011] Based on this design, the optical receiving unit further includes: a third comparator. The third comparator is configured to receive the second voltage signal output by the automatic gain controller and receive a second reference voltage signal; and output a second control signal according to the second voltage signal and the second reference voltage signal. Wherein, the second reference voltage signal is determined according to the target voltage signal of the automatic gain controller; the first difference between the first reference voltage signal and the target voltage signal is different from the second difference between the second reference voltage signal and the target voltage signal. The controlled variable current source is configured to receive the second control signal; and adjust the first differential voltage signal to a third differential voltage signal according to the second control signal. Wherein, the absolute value of the third differential voltage signal is less than the absolute value of the first differential voltage signal. The controlled variable voltage source or the controlled variable resistor is further configured to receive the second control signal; and adjust the power supply voltage signal of the differential amplification unit according to the second control signal to obtain a second input voltage signal. Wherein, the second input voltage signal serves as the target power supply voltage signal of the differential amplification unit.

[0012] In this design, when the optical receiving unit includes multiple comparators, higher-resolution control of the controlled variable current source, the controlled variable voltage source or the controlled variable resistor can be achieved. Thus, similar to the control of the controlled variable current source by multiple comparators, multiple comparators can also achieve an incremental change in the controlled variable voltage source as the offset current signal and the voltage signal output by the automatic gain controller increase. Furthermore, the reduction range of the power supply voltage of the differential amplification unit can be increased. Therefore, adjustment scenarios within a larger range can be satisfied.

[0013] In a possible design, the absolute value of the third differential voltage signal is less than the absolute value of the second differential voltage signal; the second input voltage signal is less than the first input voltage signal.

[0014] In this design, by setting different values for the reference voltages input by each comparator, incremental control of the controlled variable current source, the controlled variable voltage source or the controlled variable resistor by multiple comparators can be achieved. Thus, adjustment within a larger range can be satisfied.

[0015] In a possible design, the differential amplification unit is further configured to receive the first voltage signal and the third reference voltage signal; perform differential amplification based on the first voltage signal and the third reference voltage signal; wherein, the third reference voltage signal is determined based on the inherent DC voltage signal included in the first voltage signal.

[0016] In this design, by inputting the output signal of the transimpedance amplification unit at one end of the differential amplification unit and the inherent DC voltage signal at the other end, it is possible to cancel out the common-mode signal through the differential amplification unit, that is, to eliminate the DC signal in the optical signal path. In this way, it is further possible to adjust the remaining offset voltage through the controlled variable current source, that is, to eliminate the offset voltage. Therefore, the DCD in the optical receiving unit can be reduced, and the receiving performance of the optical receiving unit can be improved.

[0017] In a possible design, the first differential voltage signal is obtained by the difference between the first branch voltage signal and the second branch voltage signal; when the controlled variable current source is used to adjust the first differential voltage signal to the second differential voltage signal, it can include two implementation manners:

[0018] Manner A: Adjust the first branch voltage signal to obtain an adjusted first branch voltage signal; wherein, the second differential voltage signal is obtained by the difference between the adjusted first branch voltage signal and the second branch voltage signal.

[0019] Manner B: Adjust the second branch voltage signal to obtain an adjusted second branch voltage signal; wherein, the second differential voltage signal is obtained by the difference between the first branch voltage signal and the adjusted second branch voltage signal.

[0020] In this design, considering that the differential voltage signal is determined by the difference between the voltage signals output from two branches, any one of the two branches can be adjusted, so as to realize the adjustment of the differential voltage signal.

[0021] In a possible design, a driving unit; the driving unit is configured to receive the second differential voltage signal and perform load driving according to the second differential voltage signal.

[0022] In this design, by adjusting the differential voltage signal output by the differential amplification unit through the controlled variable current source, it is possible to make the differential voltage signal input to the driving unit include less or even no offset voltage, so as to reduce the DCD in the optical signal path and improve the receiving performance of the optical receiving unit.

[0023] In a possible design, a feedback unit; the feedback unit is configured to receive the output of the driving unit and output the first reference voltage signal.

[0024] In this design, by connecting a feedback unit to the output end of the driving unit, control feedback for the comparator can be achieved, thereby improving the control accuracy of the comparator.

[0025] In a possible design, the first comparator is configured to receive the first reference voltage signal, specifically: receive the first reference voltage signal provided by a voltage source externally connected to the optical receiving unit from a first port. Optionally, the external voltage source can be controlled through an external register, etc.

[0026] In this design, a flexible reference voltage signal can also be provided to the comparator through an external voltage source. It can be understood that the reference voltage signal can be determined based on the fixed DC voltage and the peak-to-peak signal voltage included in the optical signal path. In this way, the comparator can detect the offset voltage included in the output voltage signal of the transimpedance amplifier unit other than the fixed DC voltage and the peak-to-peak signal voltage.

[0027] In a possible design, the optical receiving unit further includes: a voltage source; the voltage source is configured to receive and respond to a control instruction of a control unit externally connected to the optical receiving unit and output the first reference voltage signal.

[0028] In this design, a flexible reference voltage signal can also be provided to the comparator by means of an internal voltage source and controlling the voltage source through a control unit such as an external register. It can be understood that the reference voltage signal can be determined based on the fixed DC voltage and the peak-to-peak signal voltage included in the optical signal path. In this way, the comparator can detect the offset voltage included in the output voltage signal of the transimpedance amplifier unit other than the fixed DC voltage and the peak-to-peak signal voltage.

[0029] In a possible design, the target voltage signal is obtained based on a current signal that does not include an offset current signal.

[0030] In this design, the comparator can detect the offset voltage included in the output voltage signal of the transimpedance amplifier unit other than the fixed DC voltage and the peak-to-peak signal voltage.

[0031] In each of the above designs, the absolute value of the second differential voltage signal is less than or equal to a preset voltage threshold. The absolute value of the third differential voltage signal is less than or equal to a preset voltage threshold. Optionally, the preset voltage threshold can be, for example, a relatively small voltage value.

[0032] In this design, the differential voltage output by the differential amplification unit can be adjusted to a smaller voltage value, thereby reducing the DCD in the optical receiving unit and improving the receiving performance of the optical receiving unit.

[0033] In a second aspect, an embodiment of the present application further provides an optical communication device, which may include an optical receiving unit as described in the first aspect or any possible design in the first aspect, and one or more processors. Among them, the one or more processors are used to receive and process data packets transmitted from the optical receiving unit.

[0034] Since the optical communication device in the above second aspect includes the optical receiving units of various designs in the above first aspect, it also has the technical effects that can be brought by various designs in the above first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the scenario of an optical communication system;

[0036] Figure 2 It is a schematic diagram of the structure of an optical receiving unit;

[0037] Figure 3 It is a schematic diagram of a voltage signal when there is no offset voltage provided by an embodiment of the present application;

[0038] Figure 4 It is a schematic diagram of a voltage signal when there is an offset voltage provided by an embodiment of the present application;

[0039] Figure 5A It is one of the example diagrams of an optical receiving unit 500 provided by an embodiment of the present application;

[0040] Figure 5B It is another example diagram of an optical receiving unit 500 provided by an embodiment of the present application;

[0041] Figure 6 It is an example diagram of an optical receiving unit 600 provided by an embodiment of the present application;

[0042] Figure 7 It is an example diagram of an optical receiving unit 700 provided by an embodiment of the present application;

[0043] Figure 8 It is a schematic diagram of a voltage signal after adjusting the offset voltage provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] Next, the technical solutions in the embodiments of the present application will be described in detail with reference to the drawings in the embodiments of the present application.

[0045] The optical receiver provided by the embodiments of the present application can be applied to any optical communication system that needs to receive optical signals. The optical communication system can be a point-to-multipoint (P2MP) system. The P2MP system can be a PON system or an optical transport network. For example, the PON system can be an Ethernet passive optical network (EPON) system, a gigabit-capable passive optical network (GPON) system, a wavelength division multiplexing passive optical network (WDM PON) system, an asynchronous transfer mode passive optical network (APON) system, etc. The optical transport network can be, for example, a fronthaul optical network, a backbone network, a metropolitan area network, etc.

[0046] As an example of a possible application scenario, Figure 1 is a schematic diagram of a partial scenario of an optical communication system. The PON system 100 can at least include one or more optical network units (ONUs) or optical network terminals (ONTs), and a splitter 120.

[0047] For ease of description, in this article, ONU is used to generically refer to ONT or ONU. If there are multiple ONUs, the multiple ONUs can communicate with a higher-level access device through the splitter 120. The higher-level access device can be, for example, an optical line termination (OLT) 110. For example, Figure 1 in the PON system 100, the multiple ONUs can be ONU 131, ONU 132,..., ONU 13n respectively. Each ONU can be connected to multiple users. For example, ONU 131 can be connected to user 1 and user 2; or an ONU can also be connected to one user. For example, ONU 132 can be connected to user 3, and ONU 13n can be connected to user m. In this way, the OLT 110 can provide a network-side interface for the PON system 100; the ONU can be used as a terminal device on the user side of the optical communication system, can provide a service interface for the user, and has an electro-optical conversion function to implement the signal conversion process between the user and the access network.

[0048] Generally, within the ONU, a continuous mode (CM) data from the OLT can be received through an optical receiver including a transimpedance amplifier.

[0049] In the downstream direction, the optical splitter 120 can broadcast the data from the OLT 110 to each of the ONUs 131 to 13n. The packet filters included in the ONUs can ensure that each ONU receives the correct data packets and rejects all other data packets.

[0050] It should be understood that since different ONUs are distributed at different locations, the distance between each ONU and the OLT may vary greatly. Some ONUs may be very close to the OLT, while some ONUs may be many kilometers away from the OLT. Therefore, due to the loss of the optical fiber, the amplitudes of the data packets received by the optical receivers of different ONUs may be significantly different. In addition, due to the large loss of the optical splitter, the overall amplitude level of the data packets will also be greatly reduced, and there may be significant differences in the losses of the optical splitter received by different ONUs. In this way, due to the losses caused by the optical fiber and the optical splitter 120, some ONUs may receive very large overload signals from the OLT 110, while some other ONUs receive very small sensitivity level signals. Therefore, the ratio of the overload signal to the sensitivity signal level may be very high.

[0051] Figure 2 It is a schematic structural diagram of an optical receiver. The optical receiver can be used for the ONU in an optical communication system to receive an optical signal and convert the optical signal into an electrical signal, thereby realizing signal transmission. Generally, the optical receiver can at least include:

[0052] 1) A photodetector, which is used to receive an optical signal and convert the optical signal into an electrical signal. For example, the photodetector can be Figure 2 the photodiode (PD) in.

[0053] After providing a bias voltage (assumed to be represented by V PD ) to the PD, when the provided bias voltage is greater than or equal to the threshold voltage for the normal operation of the photodiode (assumed to be represented by Vth), that is, V PD ≥V th , the photodiode can operate normally. As Figure 2 shown, V PD can be provided to the PD through the N pole of the PD to drive the PD to operate normally; the current signal (assumed to be represented by I PD ) generated after being processed by the PD can be output through the P pole of the PD, for example, transmitted to the next-stage transimpedance amplifier, etc.

[0054] Among them, I PD generally consists of an unwanted average offset current (assumed to be represented by I AV ) superimposed on a peak-to-peak signal current (assumed to be represented by I PP ). That is, IPD It can be expressed as the following formula 1:

[0055] I PD = I AV + I PP Formula 1

[0056] Wherein, I AV is caused by the offset characteristic of the photodiode, and I PP is an alternating current signal generated by the photodiode. It can be understood that, ideally, I PD is equal to I PP .

[0057] 2) A trans-impedance amplifier (TIA), which is mainly used to amplify the I PD from the PD to convert it into a single-ended voltage signal (assumed to be represented by V TIA ). Wherein, the TIA usually can at least include a trans-impedance amplification unit. In the TIA, the current signal can be amplified by the trans-impedance amplification unit; wherein, the trans-impedance amplification unit can at least include a feedback resistor unit (such as Figure 2 R fb in Figure 2 ) and a preamplifier unit (such as the amplifier in fb ). R PD can be used to provide trans-impedance gain, so as to realize the conversion of I TIA to V

[0058] Wherein, V TIA generally consists of a peak-to-peak signal voltage (assumed to be represented by V TIA-AV ) superimposed on an unwanted average offset voltage (assumed to be represented by V TIA-DC ) plus an inherent average voltage or an inherent DC voltage (assumed to be represented by V TIA-PP ). That is to say, V TIA can be expressed as the following formula 2:

[0059] V TIA = V TIA-AV + V TIA-DC + V TIA-PP Formula 2

[0060] Wherein, V TIA-AV is caused by I AV ; V TIA-DC is the inherent average voltage or the inherent DC voltage output by the TIA when I PD is 0. It should be understood that V TIA-PP is needed for V TIA ; VTIA-AV and V TIA-PP For V TIA is not needed, and part of it can be filtered by an automatic offset controller. Exemplarily, if I AV is 0, then V TIA-AV is 0, and at this time V TIA-PP will be centered on V TIA-PP Another exemplarily, if I AV is greater than 0, then V TIA-AV is also greater than 0, and at this time V TIA-PP will be centered on V TIA-AV and V TIA-PP

[0061] 3) An automatic gain control (AGC) can receive a voltage signal at any node position after the TIA, and adjust the gain and / or feedback resistance in the transimpedance amplification unit according to the voltage signal. Among them, the voltage signal output by the AGC can be represented by, for example, V AGC to represent.

[0062] In addition, it can be understood that the TIA may further include one or more levels of buffer units, and / or other one or more levels of amplification units, Figure 2 not shown.

[0063] 4) An automatic offset control (AOC) can receive a voltage signal at any node position after the TIA, and achieve offset control of the voltage signal output by the transimpedance amplification unit according to the voltage signal. Among them, the voltage signal output by the AOC can be represented by, for example, V AOC to represent. Exemplarily, part of V TIA-AV can be filtered by the AOC; in an ideal case, all of V TIA-AV can be filtered.

[0064] 5) A single-ended to differential unit (SD) can be used to convert the single-ended voltage signal from the TIA into a differential voltage signal. That is, convert V TIA into V SD

[0065] 6) A drive pulses (DRV) can be used to drive a subsequent connected load, such as the next-level unit, etc. As Figure 2 shown, the DRV can receive V SD and output V DRV

[0066] In a possible scenario, based on​​​Figure 2 For the optical receiver introduced, for a low-power optical signal applied to the PD, if the optical signal is too small to activate the AGC, a well-designed AOC will completely remove the I PP superimposed on the I AV . In this scenario, there is no offset voltage at the output terminals of the TIA, SD, and DRV included in the optical receiver.

[0067] In this scenario, the single-ended (SE) eye diagram at the output terminal of the TIA, the differential eye diagram at the output terminal of the SD, and the differential eye diagram at the output terminal of the DRV will show a duty cycle distortion (DCD) of zero. It can also be understood that the eye crossing points will be symmetric around the average of the high-amplitude level and the low-amplitude level. When the DCD is 0, the time widths of the logic high level and the logic low level are the same, that is, each has a 50% duty cycle.

[0068] For example, Figure 3 is a schematic diagram of a voltage signal when there is no offset voltage provided by an embodiment of the present application. As Figure 3 shown by the SE eye diagram of V TIA , when I PD is 0, the ideal eye crossing points level (ECPL) is equal to the inherent V TIA-DC , for example Figure 3 shown by the V TIA where the crossing point of the voltage rising edge and the voltage falling edge is 450V, that is, V TIA-DC is 450V. As Figure 3 shown by the differential eye diagram of V SD and V DRV , the ideal ECPL is 0V, that is, the crossing point of the voltage rising edge and the voltage falling edge of V SD and V DRV is 0V.

[0069] It should be understood that one of the main objectives of the AOC and AGC included in the optical receiver is to maintain the ideal ECPL within the entire input optical signal dynamic range from the sensitivity level signal to the large overload signal. The ideal ECPL can ensure the best performance of the optical receiver, and a deviation from the ideal ECPL will result in a reduction in the performance of the optical receiver. For example, if the DCD > 0, the time widths of the logic high level and the logic low level are no longer the same, resulting in a reduction in the receiver performance.

[0070] For example, Figure 4 is a schematic diagram of a voltage signal when there is an offset voltage provided by an embodiment of the present application. As Figure 4 shown by the V TIASE eye diagram, due to the existence of I AV , the remaining I AV will generate corresponding differential voltage offsets at the output of the TIA, such as Figure 4 V in TIA The ECPL of has shifted from 450V to a lower 300V. As shown in Figure 4 V shown SD and V DRV Differential eye diagram, due to the voltage offset of V TIA , as the signal propagates along the signal path, it causes significant DCD in the ECPL of SD and DRV as well. For example, Figure 4 V in SD and V DRV The horizontal dashed line in the differential eye diagram is the ideal ECPL, which is 0V, while Figure 4 The ECPL in has a large offset from 0V. Therefore, due to the existence of DCD, it will lead to a reduction in the performance of the optical receiver.

[0071] In view of this, an optical receiving unit is provided in an embodiment of the present application. The optical receiving unit can be an optical receiver, or a partial unit included in the optical receiver. The optical receiving unit can include a comparator and a controlled variable current source. Among them, the comparator compares the output voltage V AGC and the reference voltage V refC , and outputs a control signal for controlling the controlled variable current source. The controlled variable current source can control the output voltage V SD of SD, and can make V SD closer to 0V. Therefore, through the comparator and the controlled variable current source, DCD can be reduced, thereby improving the performance of the optical receiver.

[0072] In addition, the optical receiver can also include a controlled variable voltage source or a controlled variable resistor, so as to increase the adjustment range of the controlled variable current source, and further improve the reduction accuracy of DCD, achieving better performance of the optical receiver.

[0073] Figure 5A Schematic diagram of an optical receiving unit 500 provided in an embodiment of the present application. The optical receiver 500 provided in an embodiment of the present application can at least include:

[0074] (1) Photoelectric detection unit, configured to receive an optical signal and convert the optical signal into a current signal. For example, the current signal can be expressed as I PD .

[0075] Exemplarily, the photoelectric detection unit can be implemented by PD in Figure 5A . It should be noted that the specific type of the photoelectric detection unit is not limited in the embodiments of the present application.

[0076] (2) A transimpedance amplification unit, which is configured to receive a current signal from the photodetector unit and convert the current signal into a first voltage signal. For example, the first voltage signal can be expressed as V TIA .

[0077] Exemplarily, the transimpedance amplification unit can be implemented by the TIA in Figure 5A . The TIA can include a feedback resistor and an amplifier. It should be noted that the specific type and quantity of the transimpedance amplification unit are not limited in the embodiments of the present application.

[0078] (3) An automatic gain controller, which can be configured to receive the first voltage signal at any node position after the transimpedance amplification unit, and output a second voltage signal according to the first voltage signal. For example, the second voltage signal can be expressed as V AGC .

[0079] Exemplarily, the second voltage signal can be used to adjust the gain and / or feedback resistor in the transimpedance amplification unit. Another exemplarily, the second voltage signal can also be used as an input signal of the comparator 501. The function of the comparator 501 will be introduced later and will not be elaborated here for the time being. It should be noted that the specific type and quantity of the automatic gain controller are not limited in the embodiments of the present application.

[0080] (4) An automatic offset controller, which can receive the first voltage signal at any node position after the transimpedance amplification unit, and perform offset control on the voltage signal output by the transimpedance amplification unit according to the first voltage signal.

[0081] Based on Figure 3 and Figure 4 introduced above, the unnecessary V TIA included in V TIA-AV can be partially filtered out by the automatic offset controller, and the remaining unfiltered V TIA-AV will cause DCD of the output voltage signals of SD and DRV, thereby reducing the performance of the optical receiving unit. Therefore, in the embodiments of the present application, the DCD in the optical signal path can be reduced through the comparator 501 and the controlled variable current source 502, thereby improving the performance of the optical receiving unit.

[0082] (5) A differential amplification unit, which can be configured to convert the first voltage signal from the transimpedance amplification unit into a first differential voltage signal. For example, it can be expressed as V SD1 . Among them, the first voltage signal from the transimpedance amplification unit is a single-ended signal, so the differential amplification unit can also be called SD. It should be understood that V SD1 is the differential voltage signal without being adjusted by the controlled variable current source 502.

[0083] Such asFigure 5A As shown, the SD can be implemented by a general differential amplifier (DA), and the DA may include: two N-type input transistor pairs M N1 and M N2 , the resistor loads R N1 and M N2 corresponding to M N1 and R N2 , and the tail bias current sink I b . Among them,

[0084] The input terminal of R N1 can be connected to a voltage source, and the output terminal can be connected to M N1 ; similarly, the input terminal of R N2 can be connected to a voltage source, and the output terminal can be connected to M N2 . Among them, the voltage source can provide a voltage signal, for example, it can be expressed as V DD .

[0085] In addition, the output terminal of R N1 can also output a first branch voltage signal, for example, it can be expressed as V N1 ; similarly, the output terminal of R N2 can also output a second branch voltage signal, for example, it can be expressed as V N2 . It can be understood that based on the first branch voltage signal and the second branch voltage signal, the first differential voltage signal output by the differential amplification unit can be determined. For example, V SD1 can be the difference between V N1 and V N2 .

[0086] One input terminal of M N1 can be connected to R N1 , the other input terminal can be connected to the output terminal of the TIA, and the output terminal can be connected to the tail bias current sink; similarly, one input terminal of M N2 can be connected to R N2 , the other input terminal can receive the input of the third reference voltage signal V refD , and the output terminal can also be connected to the tail bias current sink. It can also be understood that the differential amplification unit receives V TIA and V refD , and differentially amplifies the single-ended voltage signal V TIA and V refD based on V TIA .

[0087] Exemplarily, V refD can be determined based on the inherent DC voltage signal included in the first voltage signal. For example, V refD = V TIA-DC. It should be understood that through the processing of the differential amplification unit, it is possible to cancel out the common-mode signal in the input signal when the differential amplification signal V SD1 is output, that is, V TIA-DC .

[0088] Among them, V refD can include various implementation manners.

[0089] For example, it can be achieved by connecting an external voltage source, and the external voltage source provides V refD .

[0090] Also for example, the optical receiving unit 500 may further include a voltage source ( refD not shown in Figure 5A ) for providing V refD . The voltage source can receive the control of an external register, so that the voltage source can provide V

[0091] through the register. Also for example, a filter ( Figure 5A not shown in TIA ) can be connected to the output end of the transimpedance amplification unit; among them, the filter can be used to filter the alternating current signal included in V TIA-DC , so that the remaining V refD can be used as V

[0092] One input end of the tail bias current sink I b can be connected to M N1 , and the other input end can be connected to M N2 , and the output end can be connected to the ground wire.

[0093] It should be noted that the input transistor pair included in SD can also be two P-type based input transistor pairs, or one P-type and one N-type input transistor pair, and the present application does not limit this.

[0094] (6) The driving unit can be used to receive the second differential voltage signal and perform load driving according to the second differential voltage signal, such as driving the next-stage unit, etc. Among them, the second differential voltage signal is a differential voltage signal obtained by adjusting the first differential voltage signal through the controlled variable current source 502, and can be expressed as V SD2 .

[0095] Among them, the aforementioned photodetection unit, transimpedance amplification unit, automatic gain controller, automatic offset controller, differential amplification unit, driving pulse can also be referred to Figure 2The content introduced therein will not be elaborated here. It should be noted that in the embodiments of the present application, it is not limited that the optical receiving unit includes the foregoing several units and their corresponding quantities and specific types. For example, it may also include other units for implementing the functions included in the optical receiving unit. For example, it may include multiple automatic gain controllers. Another example is that it may also include one or more buffer units and / or amplification units, etc.

[0096] (7) Comparator (COMP) 501, one input terminal can be connected to the output terminal of the automatic gain controller, and the other input terminal can receive the first reference voltage signal V refC1 input, and the output terminal can be connected to one input terminal of the controlled variable current source 502. Among them, V refC1 is determined according to the target voltage signal of the transimpedance amplification unit. It should be understood that the target voltage signal of the transimpedance amplification unit can be understood as the ideal output voltage signal, or it can be understood as V TIA does not include V TIA-AV , for example, V TIA can be Figure 3 450V in

[0097] In the embodiments of the present application, the comparator 501 can be used to output a first control signal according to the voltage signal V AGC output by the automatic gain controller and the target voltage signal V refC1 of the transimpedance amplification unit. For example, it can be expressed as V C1 . Among them, the first control signal V C1 can be used as the input signal of the controlled variable current source 502 to realize the control of the controlled variable current source 502.

[0098] Exemplarily, the first control signal V C1 can control the controlled variable current source 502 to work or not work. For example, when the difference between V AGC and V refC1 is greater than a preset threshold, the controlled variable current source 502 starts to work. When the difference between V AGC and V refC1 is less than or equal to the preset threshold, the controlled variable current source 502 does not start to work. It should be understood that when the difference between V AGC and V refC1 is greater than the preset threshold, it means that due to the existence of the offset current, V TIA transfers to a lower voltage level. For example, Figure 4 the V TIA shown in is 300V; at this time, the controlled variable current source 502 can be controlled to start working.

[0099] Among them, V refC1 can also include various implementation manners.

[0100] For example, it can be achieved by connecting an external voltage source, and the external voltage source provides V refC1 .

[0101] For another example, the optical receiving unit 500 may further include a voltage source for providing V refC1 (not shown in Figure 5A ), and this voltage source can receive the control of an external register, so that the voltage source can provide V through the register refC1 .

[0102] For still another example, the optical receiving unit 500 may further include a feedback unit ( Figure 5A not shown in refC ), the input end of the feedback unit can be connected to the output end of the driving unit, and the output end of the feedback unit can be connected to the input end of the comparator 501 for receiving V

[0103] (8) Controlled variable current source (I DCD ) 502, one input end can be connected to the output end of the comparator 501 to receive the first control signal V C1 output by the comparator 501; the other input end can be connected to the output end of the second branch of the differential amplification unit to receive the second branch voltage signal V N2 output by the differential amplification unit; the output end can be connected to the ground wire

[0104] In the embodiment of the present application, the controlled variable current source 502 can start working or not start working through the control of V C1 . Exemplarily, when the controlled variable current source 502 starts working, it can control the first differential voltage signal V SD1 output by the differential amplification unit. As shown in Figure 5A , the controlled variable current source 502 can control the second branch voltage signal V N2 , for example, the adjusted V N2 ' can be obtained. From the adjusted second branch voltage signal V N2 ' and the first branch voltage signal V N1 , the adjusted second differential voltage signal V SD2 can be obtained; among them, V SD2 is less than V SD1 , or V SD2 is less than or equal to a preset voltage threshold, and the preset voltage threshold can be, for example, a relatively small voltage value, so as to make V SD2 close to the ideal 0V. It should be understood that the control of the second branch voltage signal by the controlled variable current source 502 is to reduce VN1 and V N2 the difference between them, so that the DCD of V can be reduced. For example, it can be realized that the ECPL of V in SD is adjusted to be close to 0V or even equal to 0V. Figure 4 V in SD is adjusted to be close to 0V or even equal to 0V.

[0105] Based on V SD1 determined jointly by the first branch voltage signal V N1 and the second branch voltage signal V N2 Therefore, the controlled variable current source 502 can also control the first branch voltage signal V N1 For example, Figure 5B FIG. Another example diagram of the optical receiving unit 500 provided by the embodiment of the present application. Figure 5B Compared with Figure 5A , one input end of the controlled variable current source 502 can be connected not only to the second branch output end of the differential amplification unit, but also to the first branch output end of the differential amplification unit. In this way, by controlling the first branch voltage signal V N1 , it is also possible to adjust the second differential voltage signal V SD2 to be less than or equal to a preset voltage threshold. It can be understood that the preset voltage threshold can be, for example, 0V or a relatively small voltage value close to 0V.

[0106] Through Figure 5A or Figure 5B the optical receiving unit 500 introduced, by adding a comparator, it can be determined whether there is an offset voltage in the first voltage signal output by the transimpedance amplification unit. Thus, according to the comparison result, in the scenario where there is an offset voltage, the controlled variable current source 502 can be triggered to work. Then, the controlled variable current source 502 adjusts the first differential voltage signal output by the differential amplification unit, so that the adjusted second differential voltage signal can reduce the DCD, thereby improving the receiving performance of the optical receiving unit.

[0107] Figure 6 FIG. is an example diagram of an optical receiving unit 600 provided by an embodiment of the present application. Considering the operating characteristics of the differential amplifier, two transistors need to satisfy a certain voltage difference to start. Therefore, to ensure the normal operation of the differential amplification unit, the adjustment range of the controlled variable current source 502 for the first differential voltage signal has certain limitations. Taking Figure 5A as an example, Figure 6 compared with Figure 5A , the optical receiving unit 600 may further include:

[0108] (9) Controlled variable voltage source (V DCD) 601, one input terminal can be connected to the output terminal of the comparator 501 to receive the first control signal V output by the comparator 501 C1 ; the other input terminal can be connected to a voltage source to receive the power supply voltage signal V output by the voltage source DD ; the output terminal can be connected to the common input terminal of R N1 and R N2 to output the first input voltage signal, which can be expressed as V for example DD ’. For example, V DD ’ = V DD - V DCD . Among them, V DD ’ can also be understood as the voltage at node V CM , and V CM is the common-mode signal of the differential amplifier.

[0109] In the embodiment of the present application, the controlled variable voltage source 601 can also be started or not started through the control of V C1 . Exemplarily, when the controlled variable voltage source 601 is turned on, the adjustment of the power supply voltage signal V DD can be realized, which can also be understood as reducing V DD to V DD ’.

[0110] Through Figure 6 the optical receiving unit 600 introduced, by adjusting the power supply voltage signal through the controlled variable voltage source 601, the working range of the differential amplification unit can be reduced, and thus the relative pressure difference of the input transistor pair can be reduced. In this way, the adjustment range of the first differential voltage signal output by the controlled variable current source 502 to the differential amplification unit can be increased, so that more DCD can be reduced, and thus the performance of more optical receiving units can be improved.

[0111] In addition, the controlled variable voltage source 601 can also be replaced by a controlled variable resistor (R DCD ). Exemplarily, based on the controlled variable resistor, the first input voltage signal V DD ’ can be as shown in the following formula 3:

[0112] V DD ’ = V DD - (I b * R DCD ) Formula 3

[0113] Among them, I b is the current flowing through R DCD .

[0114] In addition, it should be noted that Figure 6Taking the connection of the output terminal of the second branch by the controlled variable current source 502 as an example, it is the same as Figure 5B For this type, the controlled variable current source 502 included in the optical receiving unit 600 can also be connected to the output terminal of the first branch.

[0115] Figure 7 FIG. is an exemplary diagram of an optical receiving unit 700 provided by an embodiment of the present application. Compared with Figure 6 , the optical receiving unit 700 may further include a comparator 701. The connection manner of the comparator 701 is the same as that of the comparator 501. The difference is that the other input terminal of the comparator 701 can receive the second reference voltage signal V refC2 input, and can output a second control signal, which can be expressed as V C2 for example. Among them, V C2 can also be used as the input signal of the controlled variable current source 502 to realize the control of the controlled variable current source 502; and, V C2 can also be used as the input signal of the controlled variable voltage source 601 (or controlled variable resistor) to realize the control of the controlled variable voltage source 601 (or controlled variable resistor).

[0116] Exemplarily, V refC2 > V refC1 . In this way, different comparators can output different control signals by receiving different reference voltage signals. It can be understood that when the control signals output by both comparators can control the controlled variable current source 502 to start working, the controlled variable current source 502 can adjust V SD , then the DCD of V SD is reduced more, so that the performance of the optical receiving unit can be improved more.

[0117] It should be noted that although Figure 7 shows the comparator 501 and the comparator 701, the optical receiving unit in the embodiment of the present application may further include more comparators, for example, N comparators. In this way, the N comparators can receive N different reference voltage signals V refC1 ~V refCN , and can output N different control signals V C1 ~V CN . Therefore, by detecting the magnitude relationship between V AGC and multiple different reference voltage signals by multiple comparators, higher-resolution control of the controlled variable current source 502 and the controlled variable voltage source 601 (or controlled variable resistor) can be achieved. It can be understood that the more comparators that output control signals that can control the controlled variable current source 502 to start working, the more the controlled variable current source 502 adjusts V SD , then VSD The more the DCD is reduced, the more the performance of the optical receiving unit can be improved. Additionally, it can also be understood that through multiple comparators, adjustment of a larger range of offset voltages can also be achieved.

[0118] Optionally, V refC1 ~V refCN can have a monotonically increasing relationship. For example, it can be expressed as V refCN >……>V refC2 >V refC1 . Another option is that in the embodiments of the present application, the relationship between V refC1 ~V refCN is not limited either.

[0119] In addition, it should also be noted that although Figure 7 is taken as an example in combination with Figure 6 , Figure 7 it can also be combined with Figure 5A or combined with Figure 5B .

[0120] For example, Figure 8 is a schematic diagram of a voltage signal after adjusting the offset voltage provided by the embodiments of the present application. As shown in combination with Figure 4 , Figure 8 shows the SE eye diagram of V TIA . Due to the existence of I AV , the remaining I AV will generate a corresponding differential voltage offset at the output end of the TIA. The ECPL of V TIA has shifted from 450V to a lower 300V. Compared with the differential eye diagram of V Figure 4 and V SD shown in DRV , through the processing of the optical receiving unit provided by the embodiments of the present application, the DCD of the ECPL of SD and DRV can be reduced. For example, Figure 8 in the horizontal dotted line in the differential eye diagram of V SD and V DRV is the ideal ECPL, which is 0V. Compared with the offset of the ECPL from 0V in Figure 4 , the offset of the ECPL from 0V in Figure 8 is reduced. Therefore, the optical receiving unit provided by the embodiments of the present application can reduce DCD and improve the performance of the optical receiver.

[0121] The embodiments of the present application also provide an optical receiver, which may include the optical receiving unit introduced in the foregoing embodiments and one or more other units. Among them, the one or more other units can be used to implement other functions of the optical receiving unit.

[0122] An embodiment of the present application further provides an optical communication device, which may include an optical receiving unit or an optical receiver and one or more processors as introduced in the foregoing embodiments. Wherein, the one or more processors are configured to receive and process data packets transmitted from the optical receiving unit or the optical receiver.

[0123] It should be noted that in the description of the present application, "at least one" means one or more, and multiple means two or more. In view of this, "multiple" in the embodiments of the present application can also be understood as "at least two". "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / ", unless otherwise specified, generally represents an "or" relationship between the associated objects before and after. In addition, it should be understood that in the description of the present application, terms such as "first" and "second" are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0124] It should be pointed out that "coupling" in the embodiments of the present application can be understood as electrical connection, and the coupling of two electrical components can be direct or indirect coupling between the two electrical components. For example, the connection between A and B can be either direct coupling between A and B or indirect coupling between A and B through one or more other electrical components. For example, for the coupling between A and B, it can also be direct coupling between A and C and direct coupling between C and B, and the coupling between A and B is realized through C. In some scenarios, "coupling" can also be understood as connection.

[0125] In the various embodiments of the present application, if there is no special description and logical conflict, the terms and / or descriptions between different embodiments are consistent and can be cross-referenced, and the technical features in different embodiments can be combined to form new embodiments according to their internal logical relationships.

[0126] In the present application, the word "exemplary" is used to mean being an example, illustration, or description. Any embodiment or design solution described as "exemplary" in the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Or it can be understood that the use of the word "exemplary" is intended to present concepts in a specific manner and does not constitute a limitation to the present application.

[0127] It should be understood that the various numerical numbers involved in this application are only for the convenience of description and are not used to limit the scope of the embodiments of this application. The magnitudes of the serial numbers of the above processes do not imply the sequence of execution, and the execution sequence of each process should be determined by its function and internal logic. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a series of steps or units are included. The method, system, product or device does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0128] Although the present application has been described in conjunction with specific features and their embodiments, it is obvious that various modifications and combinations can be made without departing from the spirit and scope of the present application. Accordingly, the present specification and the drawings are only exemplary illustrations of the solutions defined by the appended claims and are considered to have covered any and all modifications, variations, combinations or equivalents within the scope of the present application.

[0129] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these changes and modifications.

Claims

1. An optical receiving unit, characterized in that, Including: A photoelectric detection unit, a transimpedance amplification unit, an automatic gain controller, a differential amplification unit, a first comparator, and a controlled variable current source; The photoelectric detection unit is configured to convert a received optical signal into a current signal; The transimpedance amplification unit is configured to convert the current signal into a first voltage signal; The differential amplification unit is configured to convert the first voltage signal into a first differential voltage signal; The first comparator is configured to receive a second voltage signal output by the automatic gain controller and a first reference voltage signal; and output a first control signal according to the second voltage signal and the first reference voltage signal; wherein, the first reference voltage is determined according to a target voltage signal output by the transimpedance amplification unit; The controlled variable current source is configured to receive the first control signal; and adjust the first differential voltage signal into a second differential voltage signal according to the first control signal; wherein, the absolute value of the second differential voltage signal is less than the absolute value of the first differential voltage signal.

2. The optical receiving unit according to claim 1, wherein The optical receiving unit further includes: a controlled variable voltage source or a controlled variable resistor; The controlled variable voltage source or the controlled variable resistor is configured to receive the first control signal; and adjust a power supply voltage signal of the differential amplification unit according to the first control signal to obtain a first input voltage signal; wherein, the first input voltage signal serves as a target power supply voltage signal of the differential amplification unit.

3. The optical receiving unit according to claim 1, characterized in that, The optical receiving unit further includes: a second comparator; The second comparator is configured to receive the second voltage signal output by the automatic gain controller and a second reference voltage signal; and output a second control signal according to the second voltage signal and the second reference voltage signal; wherein, the second reference voltage signal is determined according to a target voltage signal of the automatic gain controller; a first difference between the first reference voltage signal and the target voltage signal is different from a second difference between the second reference voltage signal and the target voltage signal; The controlled variable current source is configured to receive the second control signal; and adjust the first differential voltage signal into a third differential voltage signal according to the second control signal; wherein, the absolute value of the third differential voltage signal is less than the absolute value of the first differential voltage signal.

4. The optical receiving unit according to claim 2, wherein The optical receiving unit further includes: a third comparator; The third comparator is configured to receive the second voltage signal output by the automatic gain controller and a second reference voltage signal; and output a second control signal according to the second voltage signal and the second reference voltage signal; wherein, the second reference voltage signal is determined according to a target voltage signal of the automatic gain controller; a first difference between the first reference voltage signal and the target voltage signal is different from a second difference between the second reference voltage signal and the target voltage signal; The controlled variable current source is configured to receive the second control signal; and adjust the first differential voltage signal to a third differential voltage signal according to the second control signal, wherein the third differential voltage signal is less than or equal to the first differential voltage signal. The controlled variable voltage source or the controlled variable resistor is further configured to receive the second control signal; and adjust the power supply voltage signal of the differential amplification unit according to the second control signal to obtain a second input voltage signal, wherein the second input voltage signal serves as the target power supply voltage signal of the differential amplification unit.

5. The optical receiving unit according to claim 4, wherein The absolute value of the third differential voltage signal is less than the absolute value of the second differential voltage signal. The second input voltage signal is less than the first input voltage signal.

6. The optical receiving unit according to any one of claims 1 to 5, characterized in that The differential amplification unit is further configured to receive the first voltage signal and the third reference voltage signal; and perform differential amplification according to the first voltage signal and the third reference voltage signal. Wherein, the third reference voltage signal is determined based on the inherent DC voltage signal included in the first voltage signal.

7. The optical receiving unit according to any one of claims 1 to 6, characterized in that The first differential voltage signal is obtained by the difference between the first branch voltage signal and the second branch voltage signal. When the controlled variable current source is configured to adjust the first differential voltage signal to a second differential voltage signal, specifically: Adjust the first branch voltage signal to obtain an adjusted first branch voltage signal, wherein the second differential voltage signal is obtained by the difference between the adjusted first branch voltage signal and the second branch voltage signal. Or Adjust the second branch voltage signal to obtain an adjusted second branch voltage signal, wherein the second differential voltage signal is obtained by the difference between the first branch voltage signal and the adjusted second branch voltage signal.

8. The optical receiving unit according to any one of claims 1 to 7, characterized in that, Further comprising: A driving unit; The driving unit is configured to receive the second differential voltage signal and perform load driving according to the second differential voltage signal.

9. The optical receiving unit according to claim 8, characterized in that, Further comprising: A feedback unit; The feedback unit is configured to receive the output of the driving unit and output the first reference voltage signal.

10. The optical receiving unit according to any one of claims 1 to 8, characterized in that, The first comparator is configured to receive the first reference voltage signal, specifically: Receive the first reference voltage signal provided by the voltage source externally connected to the optical receiving unit from the first port.

11. The optical receiving unit according to any one of claims 1 to 8, characterized in that, Further comprising: A voltage source; The voltage source is configured to receive and respond to the control instruction of the control unit externally connected to the optical receiving unit and output the first reference voltage signal.

12. The optical receiving unit according to any one of claims 1 to 11, characterized in that, The target voltage signal is obtained based on a current signal that does not include an offset current signal.

13. The optical receiving unit according to any one of claims 1 to 12, characterized in that, The absolute value of the second differential voltage signal is less than or equal to a preset voltage threshold.

14. An optical communication device, characterized in that, Comprising: The optical receiving unit according to any one of claims 1 to 13, and one or more processors, wherein the one or more processors are configured to receive and process the data packet transmitted from the optical receiving unit.

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