Light receiving device

Abstract

A light receiving device includes a conversion module, a signal generating module and a control module. The conversion module performs photoelectric conversion and amplification on a light signal to generate a photocurrent, the signal generating module provides a gain signal, and performs impedance conversion and amplification on the photocurrent according to an input signal indicating a predetermined output voltage swing to generate a voltage signal, and generates a measurement signal indicating an average optical power related to the light signal according to the photocurrent, and the control module outputs a variable control signal to adjust a gain of the conversion module, so that a dynamic range of the conversion module changes with the change of its own gain.

Description

Technical Field

[0001] The present invention relates to a device, in particular to a light receiving device. Background Art

[0002] The existing optical communication system includes a light transmitting device, an optical fiber, a light receiving device, an adjustable optical attenuator, a light splitter, and a light detector.

[0003] The optical transmitting device is used to transmit a multi-order pulse amplitude modulated optical signal, and transmit the optical signal to the optical splitter in sequence through the optical fiber and the adjustable optical attenuator. The optical splitter divides the received optical signal into a first optical signal and a second optical signal, and transmits the first and second optical signals to the optical detector and the optical receiving device respectively. The optical receiving device performs photoelectric conversion, amplification and demodulation on the received second optical signal to generate a digital data output for use by the subsequent digital circuit. The optical detector generates a measurement signal indicating the optical power of the optical signal based on the first optical signal, and transmits the measurement signal to the adjustable optical attenuator. The adjustable optical attenuator determines whether to perform optical power attenuation adjustment on the optical signal received through the optical fiber before outputting it to the optical splitter based on the measurement signal, so that the optical receiving device will not cause a semiconductor optical amplifier inside it to operate in a saturation region due to the excessive optical power of the second optical signal received from the optical splitter, thereby avoiding the optical receiving device from causing the digital data output generated by it to be inaccurate due to the semiconductor optical amplifier operating in the saturation region.

[0004] As a result, the existing optical communication system, in addition to the basic components such as the optical transmitter, the optical fiber and the optical receiver, also needs to include the adjustable optical attenuator, the optical splitter and the optical detector, resulting in a larger volume and higher cost for the existing optical communication system. In addition, the dynamic range of the optical receiver related to the input power of the optical signal is more limited. Therefore, there is still room for improvement in the existing optical communication system. Summary of the invention

[0005] Therefore, an object of the present invention is to provide a light receiving device that can overcome the shortcomings of the prior art.

[0006] Therefore, the optical receiving device of the present invention includes a conversion module, a signal generation module, and a control module.

[0007] The conversion module is used for receiving an optical signal from an optical fiber, and performing photoelectric conversion and amplification on the optical signal to generate a photocurrent.

[0008] The signal generating module receives an input signal indicating a predetermined output voltage swing, and is electrically connected to the conversion module to receive the photocurrent. The signal generating module provides a gain signal indicating a total gain of the module, and performs impedance conversion and amplification on the photocurrent according to the input signal to generate a voltage signal, and generates a measurement signal indicating an average optical power related to the optical signal according to the photocurrent.

[0009] The control module is electrically connected to the conversion module and the signal generating module, and outputs a variable control signal to the conversion module to adjust a gain of the conversion module, so that a dynamic range of the conversion module changes with the change of its own gain.

[0010] The technical effect of the present invention is that by generating the control signal through the control module to adjust the gain of the conversion module, the dynamic range of the conversion module can be increased accordingly, so that the distance that the optical signal can be transmitted through the optical fiber is less limited, thereby improving link performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Other features and technical effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, in which:

[0012] Figure 1 is a block diagram illustrating a first embodiment of an optical receiving device of the present invention used in an optical communication system;

[0013] Figure 2 is a simulation diagram illustrating the change of a gain of a semiconductor optical amplifier of the first embodiment with respect to an input power under different driving current conditions;

[0014] Figure 3 is a simulation diagram illustrating a change in a bit error rate with respect to an input power when the gain of the semiconductor optical amplifier of the first embodiment is a constant value;

[0015] Figure 4 is a simulation diagram illustrating a change in an extinction ratio with respect to an input power when the gain of the semiconductor optical amplifier of the first embodiment is a constant value;

[0016] Figure 5 is a simulation diagram illustrating the variation of the bit error rate with respect to the input power when the gain of the semiconductor optical amplifier of the first embodiment is not constant;

[0017] Figure 6 is a simulation diagram illustrating the variation of the extinction ratio with respect to the input power when the gain of the semiconductor optical amplifier of the first embodiment is not constant;

[0018] Figure 7 is a block diagram illustrating a second embodiment of the optical receiving device of the present invention; and

[0019] Figure 8 FIG. 1 is a block diagram illustrating a third embodiment of the optical receiving device of the present invention applied to another optical communication system.

[0020] Description of reference numerals:

[0021] 1····················Light receiving device

[0022] 10·················Optical communication system

[0023] 11, 11a, 11b...Conversion module

[0024] 111, 116··········Semiconductor optical amplifier

[0025] 112·················Optical bandpass filter

[0026] 113, 118··········Photodetector

[0027] 114·················Photoelectric converter

[0028] 115················Bias generator

[0029] 117·················Demultiplexer

[0030] 12. 12a············Signal generating module

[0031] 121·················Power detector

[0032] 122·················Transimpedance Amplifier

[0033] 123················Variable Gain Amplifier

[0034] 124···············Automatic gain controller

[0035] 125·················Signal generating unit

[0036] 13················Control module

[0037] 14··················Multi-level pulse amplitude (amplitude) demodulator

[0038] 15·················Estimation module

[0039] 2····················Light emitting device

[0040] 3···················Optical fiber

[0041] Ac·················Gain control signal

[0042] Cs················Control signal

[0043] Do················Data output

[0044] Do1~Don·········Data output

[0045] DR, DR'········Dynamic Range

[0046] Es·················Estimated signal

[0047] Gs·················Gain signal

[0048] Gs1 to Gsn··········Gain signal section

[0049] La·················Amplify optical signal

[0050] Lf··················Filtered optical signal

[0051] L1~Ln·············Adjusting optical signals

[0052] Ls··················Optical signal

[0053] Ms················Measurement signal

[0054] Ms1~Msn·········Measurement signal part

[0055] Pb··················Predetermined bit error rate threshold

[0056] Pc··················Photocurrent

[0057] Pc1~Pcn············Photocurrent section

[0058] Pt···················Preset critical value

[0059] Q··················Position

[0060] Q1···················First input power

[0061] Q2····················Second input power

[0062] Si··················Input signal

[0063] Si1~Sin············Input signal section

[0064] Va················Amplified voltage signal

[0065] Vb·················Bias voltage

[0066] Vs·················Voltage signal

[0067] Vs1~Vsn···········Voltage signal part DETAILED DESCRIPTION

[0068] Before the present invention is described in detail, it should be noted that similar elements are denoted by the same reference numerals in the following description.

[0069] <First Embodiment>

[0070] See also Figure 1 , an embodiment of the optical receiving device 1 of the present invention is applicable to an optical communication system 10. The optical communication system 10 includes an optical transmitting device 2 and an optical fiber 3. The optical transmitting device 2 is used to transmit a multi-order pulse amplitude modulation (PAM-N) optical signal Ls, and transmit the optical signal Ls to the optical receiving device 1 via the optical fiber 3. The optical signal Ls is a multi-order pulse amplitude modulation signal of at least four orders. In this embodiment, the optical signal Ls is taken as a fourth-order pulse amplitude modulation signal as an example, but it is not limited thereto.

[0071] The optical receiving device 1 of this embodiment includes a conversion module 11 , a signal generating module 12 , a control module 13 , and a multi-level pulse amplitude demodulator 14 .

[0072] The conversion module 11 is used to receive the optical signal Ls from the optical fiber 3, and perform photoelectric conversion and amplification on the optical signal Ls to generate a photocurrent Pc. In this embodiment, the conversion module 11 includes a semiconductor optical amplifier 111, an optical bandpass filter 112, and a photodetector 113 (photodetector).

[0073] The semiconductor optical amplifier 111 is used to receive the optical signal Ls and a variable control signal Cs. The semiconductor optical amplifier 111 adjusts its own gain according to the control signal Cs and amplifies the optical signal Ls to generate an amplified optical signal La. The gain of the semiconductor optical amplifier 111 serves as a gain of the conversion module 11. In detail, a driving current of the semiconductor optical amplifier 111 changes with the change of the control signal Cs, and the gain of the semiconductor optical amplifier 111 changes with the change of the driving current. For further reference, Figure 2 , which illustrates the relationship between the gain of the semiconductor optical amplifier 111 and the input power of the optical signal Ls under different driving current conditions. Figure 2 It can be seen that if a larger (smaller) gain of the semiconductor optical amplifier 111 is required, the driving current is increased (decreased) according to the control signal Cs.

[0074] The optical bandpass filter 112 is coupled to the semiconductor optical amplifier 111 to receive the amplified optical signal La and bandpass filter the amplified optical signal La to generate a filtered optical signal Lf. Specifically, the optical bandpass filter 112 is used to allow optical signals of the pre-detected wavelength to pass through and filter out optical signals of other wavelengths not to be detected.

[0075] The photodetector 113 is coupled to the optical bandpass filter 112 to receive the filtered light signal Lf, and performs photoelectric conversion on the filtered light signal Lf to form the photocurrent Pc.

[0076] The signal generating module 12 receives an input signal Si indicating a predetermined output voltage swing, and the photodetector 113 electrically connected to the conversion module 11 receives the photocurrent Pc. The signal generating module 12 provides a gain signal Gs indicating a total gain of itself. The signal generating module 12 performs impedance conversion and amplification on the photocurrent Pc according to the input signal Si to generate a voltage signal Vs, and generates a measurement signal Ms indicating an average optical power related to the optical signal Ls according to the photocurrent Pc. The measurement signal Ms serves as a received signal strength indicator (RSSI) of the optical receiving device 1. The voltage signal Vs is a multi-order pulse amplitude modulation signal of at least four orders. In the present embodiment, the voltage signal Vs is a fourth-order pulse amplitude modulation signal, but is not limited thereto. The signal generating module 12 includes a power detector 121, a impedance conversion amplifier 122, a variable gain amplifier 123, and an automatic gain controller 124.

[0077] The power detector 121 is electrically connected to the photodetector 113 to detect the photocurrent Pc and generate the measurement signal Ms accordingly.

[0078] The transimpedance amplifier 122 is electrically connected to the photodetector 113 to receive the photocurrent Pc, and performs transimpedance and amplification on the photocurrent Pc to generate an amplified voltage signal Va.

[0079] The variable gain amplifier 123 receives a gain control signal Ac indicating a variable gain, and is electrically connected to the transimpedance amplifier 122 to receive the amplified voltage signal Va. The variable gain amplifier 123 adjusts its own gain to the variable gain according to the gain control signal Ac, and amplifies the amplified voltage signal Va to generate the voltage signal Vs.

[0080] The automatic gain controller 124 receives the input signal Si and is electrically connected to the variable gain amplifier 123 to receive the voltage signal Vs. The automatic gain controller 124 provides the gain signal Gs, and the total gain indicated by the gain signal Gs is the sum of the gains of the transimpedance amplifier 122 and the variable gain amplifier 123 (herein, the automatic gain controller 124 pre-stores the gain of the transimpedance amplifier 122, and the gain of the transimpedance amplifier 122 is a constant value). The automatic gain controller 124 compares a voltage swing of the voltage signal Vs with the predetermined output voltage swing indicated by the input signal Si to adjust and generate the gain control signal Ac according to the comparison result, and outputs the gain control signal Ac to the variable gain amplifier 123. For example, when the voltage swing of the voltage signal Vs is less than the predetermined output voltage swing, the automatic gain controller 124 increases the variable gain of the gain control signal Ac, and the gain of the variable gain amplifier 123 is controlled by the gain control signal Ac and increases accordingly, so that the voltage swing of the voltage signal Vs is gradually adjusted to be equal to the predetermined output voltage swing, so as to ensure that the output size of the voltage signal Vs meets the requirements of the subsequent circuit.

[0081] The control module 13 is electrically connected to the semiconductor optical amplifier 111 of the conversion module 11 and the power detector 121 and the automatic gain controller 124 of the signal generating module 12. The control module 13 is used to receive the input signal Si and output it to the automatic gain controller 124, and also receive the gain signal Gs and the measurement signal Ms from the automatic gain controller 124 and the power detector 121, respectively. The control module 13 generates and outputs the control signal Cs to the semiconductor optical amplifier 111 at least according to the input signal Si, the gain signal Gs and the measurement signal Ms, so as to adjust the gain of the semiconductor optical amplifier 111 of the conversion module 11, so that a dynamic range of the conversion module 11 changes with the change of the gain of the semiconductor optical amplifier 111.

[0082] In detail, the control module 13 obtains an extinction ratio for determining whether the semiconductor optical amplifier 111 of the conversion module 11 operates in a saturation region according to the input signal Si, the gain signal Gs, the measurement signal Ms, and a light response related to the photoelectric conversion of the photodetector 113, and compares the extinction ratio with a preset critical value to adjust and generate the control signal Cs according to the comparison result, so that when the extinction ratio is less than the preset critical value (i.e., it means that the semiconductor optical amplifier 111 operates in the saturation region rather than a linear region, which will cause the eye diagram of the amplified optical signal La to be deformed, thereby affecting the accuracy of demodulation of the subsequent circuit), the gain of the semiconductor optical amplifier 111 is controlled by the control signal Cs to be reduced, so that the adjusted extinction ratio is greater than or equal to the preset critical value, so that the semiconductor optical amplifier 111 operates in the linear region. The extinction ratio can be obtained by the following formula (1):

[0083]

[0084] The parameter ER is the extinction ratio, the parameter Pavg is related to a ratio of the measurement signal Ms to the photoresponsivity, and the parameter Oma is related to a ratio of the input signal Si to the gain signal Gs.

[0085] The multi-level pulse amplitude demodulator 14 is electrically connected to the variable gain amplifier 123 to receive the voltage signal Vs, and demodulates the voltage signal Vs to generate a data output Do.

[0086] See also Figure 3 and Figure 4 , Figure 3 The relationship between a bit error rate (BER) of the data output Do and the input power of the optical signal Ls (which depends on the loss of the optical fiber 3) is described when the gain of the semiconductor optical amplifier 111 is a constant. Figure 4 The relationship between the extinction ratio ER and the input power of the optical signal Ls when the gain of the semiconductor optical amplifier 111 is a constant is described. Figure 3 When the bit error rate is less than or equal to a predetermined bit error rate critical value Pb, the optical communication system 10 has better link performance and preferably maximizes the dynamic range of the optical receiving device 1 (i.e., the dynamic range of the conversion module 11) over various optical fiber transmission distances. Figure 3Symbol DR). For a smaller input power of the optical signal Ls (i.e., before the Q point), the bit error rate of the data output Do is limited by the noise of the optical communication system 10, and for a larger input power of the optical signal Ls (i.e., after the Q point), the link performance of the optical communication system 10 will deteriorate, and the bit error rate of the data output Do is limited by the nonlinear distortion caused by the semiconductor optical amplifier 111 (i.e., the semiconductor optical amplifier 111 operates in the saturation region). Therefore, the input power range of the optical signal Ls for the best link performance can be obtained by adjusting the semiconductor optical amplifier 111 to operate at the starting position of the nonlinear distortion (i.e., the Q point) to maximize the dynamic range DR of the optical receiving device 1. Also, as Figure 4 As shown, for the linear operation of the amplified optical signal La, since the gain of the semiconductor optical amplifier 111 corresponding to the smaller input power of the optical signal Ls (i.e., before the Q point) changes linearly, the extinction ratio ER remains constant. However, for the larger input power of the optical signal Ls (i.e., after the Q point), since the gain of the semiconductor optical amplifier 111 gradually becomes nonlinear (i.e., the semiconductor optical amplifier 111 operates in the saturation region), the extinction ratio ER begins to be less than the preset critical value. Therefore, the optical receiving device 1 of the present invention determines whether the extinction ratio ER is less than the preset critical value (i.e., Figure 4 The semiconductor optical amplifier 111 is configured to determine whether the semiconductor optical amplifier 111 operates in the linear region, and when the extinction ratio ER is less than the preset critical value Pt, the gain of the semiconductor optical amplifier 111 is reduced (i.e., the driving current of the semiconductor optical amplifier 111 is reduced), so that the semiconductor optical amplifier 111 operates at a starting point Q of nonlinear distortion and the dynamic range of the conversion module 11 is increased, so that the distance over which the optical signal Ls can be transmitted via the optical fiber 3 is less limited, thereby improving the link transmission performance.

[0087] See also Figure 5 and Figure 6 , Figure 5 , Figure 6 Respectively Figure 3 , Figure 4 The difference is that the gain of the semiconductor optical amplifier 111 is not constant. Figure 5 and Figure 6As can be seen from the simulation diagram, when the input power of the optical signal Ls is greater than a first input power Q1, the extinction ratio ER begins to be less than the preset critical value Pt. Therefore, the control module 13 reduces the gain of the semiconductor optical amplifier 111, so that the semiconductor optical amplifier 111 continues to operate in the linear region, and the starting point of the semiconductor optical amplifier 111 from operating in the linear region to the saturation region is delayed from the position of the first input power Q1 to the position of the second input power Q2, thereby increasing a dynamic range DR' of the conversion module 11. In this way, the optical receiving device 1 of the present invention does have a preferred link performance.

[0088] It should be supplemented that, in other embodiments, the optical receiving device 1 further includes an estimation module (not shown) electrically connected between the multi-order pulse amplitude demodulator 14 and the control module 13. The estimation module generates an estimation signal (which is related to one of a bit error rate and a signal-to-noise ratio (SNR)) of the optical signal Ls according to the data output Do and outputs it to the control module 13, so that the control module 13 also adjusts the control signal Cs according to the estimation signal.

[0089] <Second Embodiment>

[0090] See also Figure 7 The second embodiment of the optical receiving device 1 of the present invention is similar to the first embodiment, except that: in the second embodiment: (1) a conversion module 11a is used to replace the conversion module 11 (see Figure 1 ), the conversion module 11a includes a photoelectric converter 114 and a bias generator 115; and (2) the power detector 121 is electrically connected to the photoelectric converter 114 instead of the photodetector 113 (see Figure 1 ).

[0091] The photoelectric converter 114 receives a bias voltage Vb and is used to receive the optical signal Ls from the optical fiber 3. The photoelectric converter 114 adjusts its own gain according to the bias voltage Vb (for example, when the bias voltage Vb increases, the gain of the photoelectric converter 114 increases accordingly), and performs photoelectric conversion and amplification on the optical signal Ls to generate the photocurrent Pc. In this embodiment, the gain of the photoelectric converter 114 is used as a gain of the conversion module 11a. The photoelectric converter 114 is made of an avalanche photodiode.

[0092] The bias generator 115 is electrically connected between the photoelectric converter 114 and the control module 13 , receives the control signal Cs from the control module 13 , adjusts and generates the bias voltage Vb according to the control signal Cs, and outputs the bias voltage Vb to the photoelectric converter 114 .

[0093] It should be noted that the control module 13 obtains the extinction ratio ER at least according to the input signal Si, the gain signal Gs, the measurement signal Ms, and a photoresponsivity related to the photoelectric conversion of the photoelectric converter 114, and in formula (1), the parameter Pavg is related to the measurement signal Ms, the photoresponsivity, and the gain of the photoelectric converter 114. The operation of the optical receiving device 1 of the second embodiment is similar to that of the optical receiving device 1 of the first embodiment, so it is not repeated here.

[0094] <Third Embodiment>

[0095] See also Figure 8 The third embodiment of the optical receiving device 1 of the present invention is used in another optical communication system, which is a wavelength division multiplexing (WDM) transmission system. The third embodiment is similar to the first embodiment, and the difference between the two is that in the third embodiment: (1) the optical signal Ls has a plurality of multi-order pulse amplitude modulation signals, each of which is at least four-order (in this embodiment, each multi-order pulse amplitude modulation signal is a four-order pulse amplitude modulation signal as an example, but not limited to this); (2) a plurality of photocurrent parts Pc1~Pcn constitute the photocurrent Pc (see Figure 1 ), a plurality of gain signal parts Gs1 to Gsn constitute the gain signal Gs (see Figure 1 ), a plurality of measurement signal parts Ms1 to Msn constitute the measurement signal Ms, a plurality of voltage signal parts Vs1 to Vsn constitute the voltage signal Vs; (3) a plurality of input signal parts Si1 to Sin constitute the input signal Si (see Figure 1 ), the plurality of input signal parts Si1-Sin respectively indicate a plurality of predetermined output voltage swing parts, the plurality of predetermined output voltage swing parts constitute the predetermined output voltage swing indicated by the input signal Si; (4) a conversion module 11b and a signal generating module 12a are used to replace the conversion module 11 and the signal generating module 12 (see FIG. 1 ) in the first embodiment respectively. Figure 1 ); and (5) also includes a plurality of multi-stage pulse amplitude demodulators 14 and an estimation module 15.

[0096] In this embodiment, the conversion module 11b includes a semiconductor optical amplifier 116, a demultiplexer 117, and a plurality of photodetectors 118. It should be noted that the operation of the semiconductor optical amplifier 116 is similar to that of the optical amplifier 116. Figure 1 The semiconductor optical amplifier 111 is similar to the semiconductor optical amplifier 111, so it will not be described here in detail.

[0097] The demultiplexer 117 is coupled to the semiconductor optical amplifier 116 to receive the amplified optical signal La, and demultiplexes the amplified optical signal La to generate a plurality of adjusted optical signals L1 -Ln of the plurality of multi-level pulse amplitude modulation signals respectively related to the optical signal Ls.

[0098] The plurality of photodetectors 118 are coupled to the demultiplexer 117 to receive the plurality of adjusted light signals L1 -Ln respectively, and perform photoelectric conversion on the plurality of adjusted light signals L1 -Ln respectively to form the plurality of corresponding photocurrent portions Pc1 -Pcn.

[0099] In this embodiment, the signal generating module 12a includes a plurality of signal generating units 125. It should be noted that the detailed component structure and operation of each signal generating unit 125 are different from those of FIG. Figure 1 The signal generating module 12 is similar to the signal generating module 12, so only the top signal generating unit 125 is taken as an example for a brief description.

[0100] The signal generating unit 125 is electrically connected to the control module 13 to receive the corresponding input signal portion Si1, and is electrically connected to the corresponding photodetector 118 to receive the corresponding photocurrent portion Pc1. The signal generating unit 125 provides the corresponding gain signal portion Gs1, and amplifies the corresponding photocurrent portion Pc1 according to the corresponding input signal portion Si1 to generate the corresponding voltage signal portion Vs1, and generates the measurement signal portion Ms1 indicating the average optical power of the corresponding photocurrent portion Pc1 according to the corresponding photocurrent portion Pc1.

[0101] The plurality of multi-step pulse amplitude demodulators 14 are electrically connected to the plurality of signal generating units 125 to receive the plurality of voltage signal parts Vs1 -Vsn, respectively, and demodulate the plurality of voltage signal parts Vs1 -Vsn to generate a plurality of data outputs Do1 -Don, respectively.

[0102] The estimation module 15 is electrically connected to the control module 13 and the plurality of multi-order pulse amplitude demodulators 14 to receive the plurality of data outputs Do1-Don, and generates an estimation signal Es according to the plurality of data outputs Do1-Don and outputs the estimation signal to the control module 13, so that the control module 13 further adjusts the control signal Cs according to the estimation signal Es. In the present embodiment, the estimation signal Es is related to one of the bit error rate and the signal-to-noise ratio of the optical signal Ls.

[0103] It should be noted that the operation of the optical receiving device 1 of the third embodiment is similar to that of the optical receiving device 1 of the first embodiment, so it will not be described in detail here. In addition, the control module 13 adjusts the control signal Cs in the following ways: (1) obtaining multiple extinction ratios to adjust the control signal Cs based on at least the multiple input signal parts Si1~Sin, the multiple gain signal parts Gs1~Gsn, and the multiple measurement signal parts Ms1~Msn; (2) obtaining the extinction ratio to adjust the control signal Cs based on only the input signal part, the gain signal part, the measurement signal part, and a corresponding light response corresponding to the output of one of the signal generating units 125; (3) adjusting the control signal Cs based only on the estimated signal Es; and (4) adjusting the control signal Cs by comprehensively considering the extinction ratio obtained by the methods (2) and (3) and the estimated signal Es, but not limited thereto.

[0104] In summary, the optical receiving device 1 of the present invention can determine whether the (said multiple) semiconductor optical amplifier 111 (116) or the photoelectric converter 114 is operating in the saturation region through the cooperation of the signal generating module 12 (12a) and the control module 13 inside the optical receiving device 1 of the present invention, and the control module 13 will perform corresponding gain control on the (said multiple) semiconductor optical amplifier 111 (116) or the photoelectric converter 114 to avoid the problem of operating in the saturation region. In this way, the optical communication system using the optical receiving device 1 of the present invention can omit the additionally required adjustable optical attenuator, the optical splitter and the optical detector in the existing optical communication system. Therefore, the optical communication system using the optical receiving device 1 of the present invention has a smaller size and lower cost than the existing optical communication system. In addition, by adjusting the gain of the (said multiple) semiconductor optical amplifiers 111 (116) or the optoelectronic converter 114, the dynamic range of the conversion module 11 (11a, 11b) can also be increased, so that the distance over which the optical signal Ls can be transmitted via the optical fiber 3 is less limited, thereby improving link performance.

[0105] The above are merely embodiments of the present invention and should not be used to limit the scope of the present invention. All simple equivalent changes and modifications made according to the claims and the patent specification of the present invention are still within the scope of the present patent.

Claims

1. A light receiving device, comprising: a conversion module, for receiving a multi-stage pulse amplitude modulated optical signal from an optical fiber, and performing photoelectric conversion and amplification on the optical signal to generate a photocurrent; a signal generating module, receiving an input signal indicating a predetermined output voltage swing, and electrically connected to the conversion module to receive the photocurrent, the signal generating module providing a gain signal indicating a total gain of the signal generating module, and performing impedance conversion and amplification on the photocurrent according to the input signal to generate a voltage signal, and generating a measurement signal indicating an average optical power related to the optical signal according to the photocurrent; and a control module, electrically connected to the conversion module and the signal generating module, and outputting a variable control signal to the conversion module according to the gain signal of the total gain and the measurement signal of the average optical power, so as to adjust a gain of the conversion module, so that a dynamic range of the conversion module changes with the change of its own gain; in, The control module is used to receive the input signal and output it to the signal generating module, and also receives the gain signal and the measurement signal from the signal generating module. The control module obtains an extinction ratio for determining whether the conversion module operates in a saturation region based on the input signal, the gain signal, the measurement signal, and a light response related to the photoelectric conversion of the conversion module, and compares the extinction ratio with a preset critical value to adjust and generate the control signal based on the comparison result, so that when the extinction ratio is less than the preset critical value, the gain of the conversion module is reduced under the control of the control signal.

2. The light receiving device according to claim 1, wherein: The conversion module includes a semiconductor optical amplifier, for receiving the optical signal from the optical fiber, and electrically connected to the control module to receive the control signal, the semiconductor optical amplifier adjusts its own gain according to the control signal, and amplifies the optical signal to generate an amplified optical signal, the gain of the semiconductor optical amplifier is used as the gain of the conversion module, an optical bandpass filter coupled to the semiconductor optical amplifier to receive the amplified optical signal and bandpass filter the amplified optical signal to generate a filtered optical signal, and A photodetector is coupled to the optical bandpass filter to receive the filtered light signal and perform photoelectric conversion on the filtered light signal to form the photocurrent.

3. The light receiving device according to claim 1, wherein: The conversion module includes a photoelectric converter, receiving a bias voltage and used to receive the optical signal from the optical fiber, the photoelectric converter adjusts its own gain according to the bias voltage, and performs photoelectric conversion and amplification on the optical signal to generate the photocurrent, the gain of the photoelectric converter serves as the gain of the conversion module, and A bias generator is electrically connected between the photoelectric converter and the control module, receives the control signal from the control module, adjusts and generates the bias voltage according to the control signal, and outputs the bias voltage to the photoelectric converter.

4. The light receiving device according to claim 3, wherein: The photoelectric converter is made of an avalanche photodiode.

5. The light receiving device according to claim 1, wherein The optical signal and the voltage signal are each a multi-level pulse amplitude modulation signal of at least four levels.

6. The light receiving device according to claim 1, wherein The signal generating module includes a power detector electrically connected to the conversion module to detect the photocurrent, and accordingly generate the measurement signal and output it to the control module, a transimpedance amplifier, electrically connected to the conversion module to receive the photocurrent, and to perform transimpedance and amplification on the photocurrent to generate an amplified voltage signal; a variable gain amplifier, receiving a gain control signal indicating a variable gain, and electrically connected to the transimpedance amplifier to receive the amplified voltage signal, the variable gain amplifier adjusting its own gain to the variable gain according to the gain control signal, and amplifying the amplified voltage signal to generate the voltage signal, and an automatic gain controller, electrically connected to the variable gain amplifier and the control module to receive the voltage signal and the input signal respectively, and compare a voltage swing of the voltage signal with the predetermined output voltage swing indicated by the input signal to adjust and generate the gain control signal according to the comparison result, and output the gain control signal to the variable gain amplifier, The automatic gain controller also provides the gain signal. The total gain indicated by the gain signal is the sum of the gains of the transimpedance amplifier and the variable gain amplifier.

7. The optical receiving device according to claim 1, further comprising: A multi-stage pulse amplitude demodulator is electrically connected to the signal generating module to receive the voltage signal and demodulate the voltage signal to generate a data output.

8. The light receiving device according to claim 1, wherein: The optical signal has a plurality of multi-order pulse amplitude modulation signals, each of which is at least four orders, the photocurrent has a plurality of photocurrent parts, and the conversion module includes a semiconductor optical amplifier, for receiving the optical signal from the optical fiber, and electrically connected to the control module to receive the control signal, the semiconductor optical amplifier adjusts its own gain according to the control signal, and amplifies the optical signal to generate an amplified optical signal, the gain of the semiconductor optical amplifier is used as the gain of the conversion module, a demultiplexer coupled to the semiconductor optical amplifier to receive the amplified optical signal and demultiplex the amplified optical signal to generate a plurality of adjusted optical signals respectively related to the plurality of multi-level pulse amplitude modulation signals, and A plurality of photodetectors are coupled to the demultiplexer to respectively receive the plurality of adjustment light signals and respectively perform photoelectric conversion on the plurality of adjustment light signals into the corresponding plurality of photocurrent parts.

9. The light receiving device according to claim 8, wherein: The predetermined output voltage swing has a plurality of predetermined output voltage swing parts, the input signal has a plurality of input signal parts each indicating a corresponding one of the plurality of predetermined output voltage swing parts, the gain signal has a plurality of gain signal parts, the voltage signal has a plurality of voltage signal parts, and the signal generating module includes A plurality of signal generating units, each signal generating unit is electrically connected to the control module to receive the corresponding input signal portion, and is electrically connected to the corresponding photodetector to receive the corresponding photocurrent portion, each signal generating unit provides the corresponding gain signal portion, and amplifies the corresponding photocurrent portion according to the corresponding input signal portion to generate the corresponding voltage signal portion, and generates a measurement signal portion indicating the average optical power of the corresponding photocurrent portion according to the corresponding photocurrent portion, wherein a plurality of measurement signal portions constitute the measurement signal.

10. The optical receiving device according to claim 9, further comprising: a plurality of multi-stage pulse amplitude demodulators, respectively electrically connected to the plurality of signal generating units to respectively receive the plurality of voltage signal parts, and respectively demodulate the plurality of voltage signal parts to respectively generate a plurality of data outputs; and an estimation module electrically connected to the control module and the plurality of multi-order pulse amplitude demodulators to receive the plurality of data outputs, and to generate an estimation signal according to the plurality of data outputs and output the estimation signal to the control module, so that the control module further adjusts the control signal according to the estimation signal, wherein the estimation signal is related to one of a bit error rate and a signal-to-noise ratio of the optical signal.

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