CN215378930U

CN215378930U - Long-distance optical module based on PAM4 modulation

Info

Publication number: CN215378930U
Application number: CN202121368225.4U
Authority: CN
Inventors: 孔令桥; 卜勤练; 崔子伦; 穆磊
Original assignee: Accelink Technologies Co Ltd
Current assignee: Accelink Technologies Co Ltd
Priority date: 2021-06-18
Filing date: 2021-06-18
Publication date: 2021-12-31
Anticipated expiration: 2031-06-18

Abstract

The utility model relates to the field of optical communication, in particular to a PAM4 modulation-based long-distance optical module. The optical transceiver comprises an interface unit, an optical transmitting unit, an optical receiving unit and a DSP processing unit, wherein the interface unit is connected with a first port of the DSP processing unit, a second port of the DSP processing unit is connected with an input port of the optical transmitting unit, and a third port of the DSP processing unit is connected with an output port of the optical receiving unit; the optical receiving unit comprises a quasi-coherent special chip, and an output port of the quasi-coherent special chip is used as an output port of the optical receiving unit; the external electrical interface of the interface unit is used as the external electrical interface of the optical module, the optical output port is used as the external optical output port of the optical module, and the optical input port of the optical receiving unit is used as the external optical input port of the optical module. Under the condition of not increasing the baud rate, the bit rate of the optical transceiver module is doubled, the transmission rate and the distance are increased, and the problems of high complexity and high cost of common coherent detection are solved.

Description

Long-distance optical module based on PAM4 modulation

[ technical field ] A method for producing a semiconductor device

The utility model relates to the field of optical communication, in particular to a PAM4 modulation-based long-distance optical module.

[ background of the utility model ]

With the arrival of the 5G commercial era, the network traffic and data will meet the explosive growth, which will certainly put higher requirements on the optical fiber communication system. How to achieve higher transmission rates and longer transmission distances has also become the main direction of current research. Unfortunately, as transmission rates increase, the impact of chromatic dispersion in fiber optic communication systems increases, and transmission distances are correspondingly more limited.

Currently, a network based on 10Gbps generally operates in the C-band, so as to use Dense Wavelength Division Multiplexing (DWDM) technology over a distance exceeding 20 km. The simplest way to upgrade an existing optical fiber communication network is to directly upgrade an optical module, for example, to replace a 10G optical module in the system with an optical module of 25G or higher speed. However, due to the limitation of dispersion, the maximum transmission distance of the current 25G optical module based on NRZ modulation is only 10-15km in the C-band, and if an optical module with higher speed is used, the corresponding transmission distance is shorter.

In view of this, how to overcome the defects existing in the prior art and reduce the influence of chromatic dispersion on the transmission distance of the optical module is a problem to be solved in the field of the technology.

[ Utility model ] content

Aiming at the defects or improvement requirements of the prior art, the utility model solves the problem that the transmission distance of the existing high-rate optical module is limited due to chromatic dispersion.

The embodiment of the utility model adopts the following technical scheme:

the utility model provides a long distance optical module based on PAM4 modulation, including interface unit 10, light emission unit 30 and light receiving unit 40: the optical transceiver further comprises a DSP processing unit 20, wherein the interface unit 10 is connected with a first port of the DSP processing unit 20, a second port of the DSP processing unit 20 is connected with an input port of the light emitting unit 30, and a third port of the DSP processing unit 20 is connected with an output port of the light receiving unit 40; the light receiving unit 40 includes a chip 41 dedicated to quasi-coherence, and an output port of the chip 41 dedicated to quasi-coherence serves as an output port of the light receiving unit 40; the external electrical interface of the interface unit 10 serves as an external electrical interface of the optical module, the optical output port of the optical transmitting unit 30 serves as an external optical output port of the optical module, and the optical input port of the optical receiving unit 40 serves as an external optical input port of the optical module.

Preferably, the optical transmitting unit 30 includes a laser 31, an external modulator 32 and a driving circuit 33, specifically: an input interface of the laser 31 serves as an input port of the optical transmitting unit 30, an output port of the laser 31 is coupled with an input port of the external modulator 32, a control port of the external modulator 32 is connected with the driving circuit 33, and an output port of the external modulator 32 serves as an optical output port of the optical transmitting unit 30.

Preferably, the light receiving unit 40 further includes a local oscillator light input port 42, an optical coupler 43, a polarization beam splitter 44, and a light detecting unit 45, specifically: the input port of the semi-coherent special chip 41 is coupled with the output port of the first optical detection unit 45; the input port of the first light detection unit 45 is coupled to the output light of the polarizing beam splitter 44; a first input port of the optical coupler 43 serves as an optical input port of the optical receiving unit 40, a second input port of the optical coupler 43 is coupled to a first side of the local oscillation optical input port 42, and an output port of the optical coupler 43 is connected to an input port of the polarization beam splitter 44.

Preferably, the light detection unit 45 includes a photodetector 46 and a transimpedance amplifier 47, specifically: each transimpedance amplifier 47 comprises a set of output ports, each set of output ports being coupled to a set of input ports of the quasi-coherent special chip 41; each transimpedance amplifier 47 comprises a set of input ports and each photodetector 46 comprises a set of output ports, the output ports of transimpedance amplifiers 47 being coupled to the input ports of photodetectors 46 and the input ports of photodetectors 46 being coupled to the output ports of optical couplers 43.

Preferably, the optical receiving unit 40 further includes a local oscillator laser 48, specifically: an optical output port of the local oscillator laser 48 is coupled to a second side of the local oscillator optical input port 42.

Preferably, the light emitting unit 30 further includes a beam splitter 34, specifically: an input port of the optical splitter 34 is connected to an output port of the laser 31, a first output port of the optical splitter 34 is connected to an input port of the external modulator 32, and a second port of the optical splitter 34 is coupled to a second side of the local oscillator optical input port 42.

Preferably, the light receiving unit 40 includes a first light detecting unit 45-1 and a second light detecting unit 45-2, specifically: an output port of the first optical detection unit 45-1 is coupled to a first input port of the quasi-coherent special chip 41, and an input port of the first optical detection unit 45-1 is optically coupled to a first output port of the polarization beam splitter 44; an output port of the second optical detection unit 45-2 is coupled to a second input port of the quasi-coherent dedicated chip 41, and an input port of the second optical detection unit 45-2 is optically coupled to a second output of the polarization beam splitter 44.

Preferably, the light emitting unit 30 includes a driving circuit 33, a first laser 31-1, a second laser 31-2, a first external modulator 32-1, a second external modulator 32-2, a first optical splitter 34-1 and a second optical splitter 34-2, the first laser 31-1, the first optical splitter 34-1 and the first external modulator 32-1 are connected in sequence, the second laser 31-2, the second optical splitter 34-2 and the second external modulator 32-2 are connected in sequence, and control ports of the first external modulator 32-1 and the second external modulator 32-2 are connected to the driving circuit 33, respectively; the light receiving unit 40 includes a quasi-coherent special chip 41, a first local oscillation light input port, a second local oscillation light input port, a first optical coupler 43-1, a second optical coupler 43-2, a first polarization beam splitter 44-1, a second polarization beam splitter 44-2, a third light detecting unit, a fourth light detecting unit, a fifth light detecting unit and a sixth light detecting unit, the first optical coupler 43-1 is connected with the first polarization beam splitter 44-1, the third light detecting unit and the fourth light detecting unit are respectively coupled with two output light paths of the first polarization beam splitter 44-1, the second optical coupler 43-2 is connected with the second polarization beam splitter 44-2, the fifth light detecting unit and the sixth light detecting unit are respectively coupled with two output light paths of the second polarization beam splitter 44-2, the third light detecting unit, The fourth optical detection unit, the fifth optical detection unit and the sixth optical detection unit are respectively coupled to a group of ports of the semi-coherent special chip 41; the second port of the first optical splitter 34-1 is coupled to the second side of the first local oscillator optical input port, the first optical coupler 43-1 is coupled to the first side of the first local oscillator optical input port, the second port of the second optical splitter 34-2 is coupled to the second side of the second local oscillator optical input port, and the second optical coupler 43-2 is coupled to the first side of the second local oscillator optical input port.

Compared with the prior art, the embodiment of the utility model has the beneficial effects that: at the transmitting end, by using a Digital Signal Processing (DSP) Processing unit and adopting a higher-order Modulation technique such as a 4-level Pulse Amplitude Modulation code (PAM 4) than a Non-Return to Zero (NRZ) code used in the existing network, the bit rate of the optical transceiver module can be doubled without increasing the baud rate, and the transmission rate is increased. At the receiving end, by using the chip dedicated for quasi-coherent and adopting the quasi-coherent receiving technology, the influence of chromatic dispersion on the transmission signal can be effectively reduced, so that the transmission distance is longer and reaches 30 km-40 km, and the problems of high complexity and high cost of common coherent detection are avoided.

[ description of the drawings ]

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the utility model, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

Fig. 1 is a schematic structural diagram of a long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of another long-distance optical module based on PAM4 modulation according to an embodiment of the present invention;

wherein the reference numbers are as follows:

10: interface unit, 20: a DSP processing unit for processing the received signals,

30: light emitting unit, 31: laser, 31-1: first laser, 31-2: second laser, 32: external modulator, 32-1: first external modulator, 32-2: second external modulator, 33: drive circuit, 34: spectrometer, 34-1: first beam splitter, 34-2: a second beam splitter;

40: light receiving unit, 41: quasi-coherent specialized chip, 42: local oscillator optical input port, 43: optical coupler, 43-1: first optical coupler, 43-2: second optical coupler, 44: polarizing beam splitter, 44-1: first polarizing beam splitter, 44-2: second polarization beam splitter, 45: light detection unit, 45-1: first light detection unit, 45-2: second light detection unit, 46: photodetector, 47: transimpedance amplifier, 48: and a local oscillator laser.

[ detailed description ] embodiments

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

The present invention is a system structure of a specific function system, so the functional logic relationship of each structural module is mainly explained in the specific embodiment, and the specific software and hardware implementation is not limited.

In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other. The utility model will be described in detail below with reference to the figures and examples.

Example 1:

in order to solve the problem that the use distance of the C-band high-speed optical module is too short, embodiments of the present invention provide an optical transceiver module based on quasi-coherent reception and PAM4 modulation. PAM4 modulation is realized through the DSP processing unit 20, and a quasi-coherent technology is realized through the quasi-coherent special chip 41, so that the dispersion of the optical module is reduced, and the transmission distance of the optical module is increased.

The following describes a specific structure of a long-distance optical module based on PAM4 modulation according to the present invention with reference to fig. 1.

The optical module provided by the present embodiment includes an interface unit 10, a DSP processing unit 20, a light emitting unit 30, and a light receiving unit 40.

An external electrical interface of the interface unit 10 is used as an external electrical interface of the optical module, and the interface unit 10 is connected to a first port of the DSP processing unit 20. The interface unit 10 is used as an electrical interface of the optical module, and is configured to connect the DSP processing unit 20 and an external device, input a high-speed electrical signal of the external device to the DSP processing unit 20, and input a high-speed electrical signal output by the DSP processing unit 20 to the external device.

A second port of the DSP processing unit 20 is connected to an input port of the light emitting unit 30, and a third port of the DSP processing unit 20 is connected to an output port of the light receiving unit 40. The DSP processing unit 20 converts the NRZ encoded electrical signal transmitted from the interface unit 10 into a PAM4 encoded electrical signal, performs equalization processing, and inputs the result to the optical transmission unit 30. The DSP processing unit 20 also performs equalization processing on the PAM4 electrical signal generated by the optical receiving unit 30, converts the electrical signal into an NRZ encoded electrical signal, and inputs the NRZ encoded electrical signal to the interface unit 10. Meanwhile, the DSP processing unit 20 may also perform clock recovery, amplification, equalization, demodulation, and the like on the signal.

The optical input port of the optical receiver unit 40 is used as an external optical input port of the optical module, and the received high-speed optical signal is converted into a high-speed electrical signal and input to the DSP unit 20 for processing. The optical receiving unit 40 includes a quasi-coherent Specific Integrated Circuit (ASIC) 41, an output port of the quasi-coherent Specific chip 41 is used as an output port of the optical receiving unit 40, and quasi-coherent reception is realized by the quasi-coherent Specific chip 41.

The optical output port of the optical transmitting unit 30 serves as an external optical output port of the optical module, and converts the high-speed electrical signal processed by the DSP unit 20 into a high-speed optical signal and outputs the high-speed optical signal.

In a specific implementation, as shown in fig. 2, a specific structure of the light emitting unit 30 and the light receiving unit 40 in a usable light module structure is provided. Other receiving methods capable of satisfying the light emitting function of the optical module of the present embodiment may be used, and the light receiving unit 40 needs to include the chip 41 dedicated to quasi-coherence. In the embodiment, the baud rate of signal modulation is 25G/s as an example, the bit rate of the output PAM4 signal after modulation is 50G/s, the long-distance transmission requirement of 50G/s can be met, and other baud rates can be used according to the requirement in practical use.

The light emitting unit 30 includes a laser 31, an external modulator 32, and a driving circuit 33. An input interface of the laser 31 serves as an input port of the optical transmitting unit 30, an output port of the laser 31 is coupled with an input port of the external modulator 32, a control port of the external modulator 32 is connected with the driving circuit 33, and an output port of the external modulator 32 serves as an optical output port of the optical transmitting unit 30. An optical signal emitted by the laser 31 enters the external modulator 32, the driving circuit 33 controls the external modulator 32 to modulate the optical signal according to the signal output by the DSP unit 20, and the modulated PAM4 optical signal is output from the external optical output port of the optical module.

The optical receiving unit 40 includes the optical receiving unit 40, and further includes a quasi-coherent dedicated chip 41, a local oscillator light input port 42, an optical coupler 43, a polarization beam splitter 44, and an optical detection unit 45. An input port of the semi-coherent dedicated chip 41 is coupled to an output port of the first optical detection unit 45. The input port of the first light detection unit 45 is coupled to the output light of the polarizing beam splitter 44. A first input port of the optical coupler 43 serves as an optical input port of the optical receiving unit 40, a second input port of the optical coupler 43 is coupled to a first side of the local oscillation optical input port 42, and an output port of the optical coupler 43 is connected to an input port of the polarization beam splitter 44. An optical signal is received and enters the optical module through an external optical input port, a local oscillator optical signal enters the optical module through a local oscillator optical input port 42, the received optical signal and the local oscillator optical signal enter an optical coupler 43 and are coupled into a beam of optical signal, the coupled optical signal enters a polarization beam splitter 44 and is subjected to polarization beam splitting to output two orthogonal linearly polarized light beams, the two linearly polarized light beams are converted into high-speed electric signals after passing through an optical detection unit 45, the signals are processed through a quasi-coherent special chip 41, and finally the signals enter a DSP processing unit 20.

As shown in fig. 3, the optical detection unit 45 includes a Photodetector (PD) 46 and transimpedance amplifiers (TIA) 47, where each transimpedance Amplifier 47 includes a set of output ports, and each set of output ports is coupled to a set of input ports of the quasi-coherent special chip 41. Each transimpedance amplifier 47 comprises a set of input ports and each photodetector 46 comprises a set of output ports, the output ports of transimpedance amplifiers 47 being coupled to the input ports of photodetectors 46 and the input ports of photodetectors 46 being coupled to the output ports of optical couplers 43. Conversion of an optical signal to an electrical signal, and amplification of the electrical signal, may be accomplished through a functional combination of PD 46 and TIA 47.

The optical transceiver module provided in fig. 2 adopts PAM4 modulation technology at the transmitting end, can transmit 50G PAM4 signals, and adopts quasi-coherent reception technology at the receiving end, so that a C-band long-distance 50G optical module can be realized, and 50G long-distance transmission can be realized.

Further, in the optical module provided in fig. 2, the local oscillation optical signal is provided by the optical receiving module 40, and may also be provided by the optical transmitting unit 30.

When the local oscillator optical signal is provided by the optical receiving unit 40, the optical receiving unit 40 also includes a local oscillator laser 48. As shown in fig. 4, an optical output port of the local oscillator laser 48 is coupled to a second side of the local oscillator optical input port 42 to provide the local oscillator optical signal through the local oscillator optical input port 42. In particular use, to ensure that the received optical signal matches the local oscillator optical signal, the local oscillator laser 48 should generate a local oscillator optical signal having a frequency that matches the received optical signal, maintaining a frequency difference of 50GHz from the received optical signal. In specific implementation, the frequency of the local oscillator laser 48 may be adjusted in real time according to the difference of the received optical signals, or the frequency of the local oscillator laser 48 may be fixed, and the local oscillator optical signal sent by the local terminal is transmitted to the optical module at the opposite terminal in a pair-to-pair manner by the two optical modules, so as to ensure that the received optical signal matches the local oscillator optical signal in frequency.

When the local oscillation light is supplied from the optical transmitting unit 30, the optical transmitting unit 30 further includes an optical splitter 34, and the light split by the optical splitter 34 is used as the local oscillation light. As shown in fig. 5, an input port of the optical splitter 34 is connected to an output port of the laser 31, a first output port of the optical splitter 34 is connected to an input port of the external modulator 32, and a second port of the optical splitter 34 is coupled to a second side of the local oscillator optical input port 42. The optical splitter 34 splits the optical signal emitted by the laser 31 in the optical transmitting unit 30 into two paths, and one path is still modulated by the external modulator 32 to be used as the emitted optical signal; the other path enters the optical receiving unit 40 as a local oscillation optical signal. In this scenario, in order to ensure that the output power of the laser 31 can satisfy the requirements of transmitting optical signals and local oscillator optical signals at the same time, the laser 31 needs to use a high-power laser.

Further, in the optical module shown in fig. 2, two sets of optical detection units 45 may be used to detect the received optical signal and the local oscillator optical signal, respectively. Specifically, as shown in fig. 6, the light receiving unit 40 includes a first light detecting unit 45-1 and a second light detecting unit 45-2. An output port of the first optical detection unit 45-1 is coupled to a first input port of the quasi-coherent special chip 41, and an input port of the first optical detection unit 45-1 is optically coupled to a first output port of the polarization beam splitter 44 to form a first detection optical path. An output port of the second optical detection unit 45-2 is coupled to a second input port of the quasi-coherent special chip 41, and an input port of the second optical detection unit 45-2 is optically coupled to a second output port of the polarization beam splitter 44 to form a second detection optical path. The first detection optical path and the second detection optical path respectively detect the received optical signal and the local oscillator optical signal.

As for the optical module provided in fig. 6, the local oscillation optical signal is provided by the optical receiving module 40, and may also be provided by the optical transmitting unit 30. When the local oscillator optical signal is provided by the optical receiver unit 40, as shown in fig. 6, the optical receiver unit 40 further includes a local oscillator laser 48, and an optical output port of the local oscillator laser 48 is coupled to the second side of the local oscillator optical input port 42. When the local oscillator light is provided by the optical transmitting unit 30, as shown in fig. 7, the optical transmitting unit 30 further includes an optical splitter 34, an input port of the optical splitter 34 is connected to an output port of the laser 31, a first output port of the optical splitter 34 is connected to an input port of the external modulator 32, and a second port of the optical splitter 34 is coupled to a second side of the local oscillator light input port 42. Both of these ways may provide a usable local oscillator optical signal to the optical receiving unit 40.

In order to improve the transmission rate of the optical module, on the basis of the optical module provided in fig. 6, the optical module provided in this embodiment may also use a dual-channel mode, and provide twice the transmission rate through two sets of lasers 31 and two sets of optical detection units 45.

As shown in fig. 9, the light emitting unit 30 includes a driving circuit 33, a first laser 31-1, a second laser 31-2, a first external modulator 32-1, a second external modulator 32-2, a first optical splitter 34-1, and a second optical splitter 34-2, and the first laser 31-1, the first optical splitter 34-1, and the first external modulator 32-1 are connected in this order. The first laser 31-1 emits an unmodulated optical signal into the first optical splitter 34-1, which is split into two beams. The first beam of light enters the first external modulator 32-1 as an emitted light signal, and the first external modulator 32-1 is controlled by the driving circuit 33 according to the DSP processing unit 20 to modulate a PAM4 signal with a bit rate of 50G/s; the second beam of light enters the first local oscillator light input port of the light receiving unit 40 as a local oscillator light signal. The second laser 31-2, the second optical splitter 34-2 and the second external modulator 32-2 are connected in sequence, and control ports of the first external modulator 32-1 and the second external modulator 32-2 are connected to the driving circuit 33, respectively. Similarly, the unmodulated optical signal emitted by the second laser 31-2 enters the second optical splitter 34-2 and is split into two beams, the first beam enters the second external modulator 32-2 as the transmitted optical signal, and the second external modulator 32-2 is controlled by the driving circuit 33 according to the DSP processing unit 20 to modulate the signal into a PAM4 signal with a bit rate of 50G/s; the second beam of light enters the second local oscillator light input port of the light receiving unit 40 as a local oscillator light signal. In order to ensure that the local oscillator optical signal frequency matches the received optical signal, the optical signals emitted by the first laser 31-1 and the second laser 31-2 should maintain a frequency difference of 50 GHz. Meanwhile, in order to ensure that the output power of the first laser 31-1 and the second laser 31-2 can simultaneously meet the requirements of transmitting optical signals and local oscillation optical signals, the first laser 31-1 and the second laser 31-2 need to use high-power lasers. On the other hand, in order to ensure signal quality of two channels, the driving circuit 33 may further include an amplifying circuit for amplifying a signal.

The light receiving unit 40 includes a quasi-coherent special chip 41, a first local oscillation light input port, a second local oscillation light input port, a first optical coupler 43-1, a second optical coupler 43-2, a first polarization beam splitter 44-1, a second polarization beam splitter 44-2, a third light detecting unit, a fourth light detecting unit, a fifth light detecting unit and a sixth light detecting unit, the first optical coupler 43-1 is connected with the first polarization beam splitter 44-1, the third light detecting unit and the fourth light detecting unit are respectively coupled with two output light paths of the first polarization beam splitter 44-1, the second optical coupler 43-2 is connected with the second polarization beam splitter 44-2, the fifth light detecting unit and the sixth light detecting unit are respectively coupled with two output light paths of the second polarization beam splitter 44-2, the third light detecting unit, the sixth light detecting unit, The fourth optical detection unit, the fifth optical detection unit and the sixth optical detection unit are respectively coupled to a set of ports of the semi-coherent special chip 41.

The second port of the first optical splitter 34-1 is coupled to the second side of the first local oscillator optical input port, the first optical coupler 43-1 is coupled to the first side of the first local oscillator optical input port, the second port of the second optical splitter 34-2 is coupled to the second side of the second local oscillator optical input port, and the second optical coupler 43-2 is coupled to the first side of the second local oscillator optical input port.

An unmodulated optical signal output by the second optical splitter 34-2 and a received optical signal simultaneously enter the first optical coupler 43-1 to be coupled together, an optical signal output from the first optical coupler 43-1 enters the first polarization beam splitter 44-1, and is split into two orthogonal linearly polarized light beams by the polarization beam splitter 44-1; the two beams of light enter the PDs and their corresponding TIAs in the third optical detection unit and the fourth optical detection unit, respectively, are converted into two electrical signals, which enter the chip 41 dedicated for quasi-coherence to be processed, and the electrical signals processed by the chip 41 dedicated for quasi-coherence then enter the DSP processing unit 20.

Similarly, an unmodulated optical signal output from the first optical splitter 34-1 enters the second optical coupler 43-2 simultaneously with the received optical signal 1 and is coupled together, and an optical signal output from the second optical coupler 43-2 enters the second polarization beam splitter 44-2 and is split into two orthogonal linearly polarized light beams by the second polarization beam splitter 44-2. The two beams of light enter the two PDs of the fifth optical detection unit and the sixth optical detection unit and the corresponding TIAs thereof respectively, are converted into two beams of electrical signals, enter the chip 41 dedicated for quasi-coherence to be processed, and the electrical signals processed by the chip 41 dedicated for quasi-coherence enter the DSP processing unit 20.

The dual-channel optical module provided in fig. 9 has two light emitting ends and two light receiving ends, and can simultaneously transmit two paths of PAM4 signals with a bit rate of 50G/s, that is, can realize a C-band long-distance 100G optical module.

Compared with the common direct detection technology, the PAM4 modulation technology and the quasi-coherent receiving technology provided by the embodiment can effectively reduce the influence of dispersion on the transmission distance, so that the transmission distance of the optical module in the C wave band is obviously improved.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A PAM4 modulation-based long-distance optical module, comprising: an interface unit (10), a light emitting unit (30) and a light receiving unit (40), characterized in that:

the optical fiber cable further comprises a DSP (digital signal processor) processing unit (20), wherein the interface unit (10) is connected with a first port of the DSP processing unit (20), a second port of the DSP processing unit (20) is connected with an input port of the optical transmitting unit (30), and a third port of the DSP processing unit (20) is connected with an output port of the optical receiving unit (40);

the light receiving unit (40) comprises a quasi-coherent special chip (41), and an output port of the quasi-coherent special chip (41) is used as an output port of the light receiving unit (40);

an external electrical interface of the interface unit (10) serves as an external electrical interface of the optical module, an optical output port of the optical transmitting unit (30) serves as an external optical output port of the optical module, and an optical input port of the optical receiving unit (40) serves as an external optical input port of the optical module.

2. Long-distance optical module based on PAM4 modulation according to claim 1, characterized in that the light emitting unit (30) comprises a laser (31), an external modulator (32) and a driving circuit (33), in particular:

an input interface of the laser (31) is used as an input port of the light emitting unit (30), an output port of the laser (31) is coupled with an input port of the external modulator (32), a control port of the external modulator (32) is connected with the driving circuit (33), and an output port of the external modulator (32) is used as an optical output port of the light emitting unit (30).

3. The PAM4 modulation-based long-distance optical module of claim 2, wherein the optical receiving unit (40) further comprises a local oscillator light input port (42), an optical coupler (43), a polarization beam splitter (44), and an optical detection unit (45), and specifically:

the input port of the quasi-coherent special chip (41) is coupled with the output port of the optical detection unit (45);

an input port of the light detection unit (45) is coupled with the output light of the polarization beam splitter (44);

a first input port of the optical coupler (43) is used as an optical input port of the optical receiving unit (40), a second input port of the optical coupler (43) is coupled with a first side of the local oscillator light input port (42), and an output port of the optical coupler (43) is connected with an input port of the polarization beam splitter (44).

4. The PAM4 modulation based long-distance optical module of claim 3, wherein the optical detection unit (45) comprises a photodetector (46) and a transimpedance amplifier (47), in particular:

each transimpedance amplifier (47) comprising a set of output ports, each set of output ports being coupled to a set of input ports of a quasi-coherent dedicated chip (41);

each transimpedance amplifier (47) comprises a set of input ports, each photodetector (46) comprises a set of output ports, the output ports of the transimpedance amplifiers (47) are coupled to the input ports of the photodetectors (46), and the input ports of the photodetectors (46) are coupled to the output ports of the optical couplers (43).

5. The PAM4 modulation-based long-distance optical module of claim 4, wherein the optical receiving unit (40) further comprises a local oscillator laser (48), specifically:

an optical output port of the local oscillator laser (48) is coupled to a second side of the local oscillator optical input port (42).

6. The PAM4 modulation based long-distance light module of claim 4, wherein the light emitting unit (30) further comprises a beam splitter (34), in particular:

an input port of the optical splitter (34) is connected with an output port of the laser (31), a first output port of the optical splitter (34) is connected with an input port of the external modulator (32), and a second port of the optical splitter (34) is coupled with a second side of the local oscillator optical input port (42).

7. The PAM4 modulation based long-distance optical module of claim 4, wherein the light receiving unit (40) comprises a first light detection unit (45-1), a second light detection unit (45-2), in particular:

an output port of the first optical detection unit (45-1) is coupled with a first input port of the quasi-coherent special chip (41), and an input port of the first optical detection unit (45-1) is optically coupled with a first output port of the polarization beam splitter (44);

an output port of the second optical detection unit (45-2) is coupled to a second input port of the quasi-coherent specialized chip (41), and an input port of the second optical detection unit (45-2) is optically coupled to a second output of the polarization beam splitter (44).

8. The PAM4 modulation-based long-distance optical module of claim 7, wherein the optical receiving unit (40) further comprises a local oscillator laser (48), specifically:

9. The PAM4 modulation based long-distance light module of claim 7, wherein the light emitting unit (30) further comprises a beam splitter (34), in particular:

10. The PAM4 modulation based long-distance optical module of claim 3, wherein:

the light emitting unit (30) comprises a driving circuit (33), a first laser (31-1), a second laser (31-2), a first external modulator (32-1), a second external modulator (32-2), a first optical splitter (34-1) and a second optical splitter (34-2), wherein the first laser (31-1), the first optical splitter (34-1) and the first external modulator (32-1) are sequentially connected, the second laser (31-2), the second optical splitter (34-2) and the second external modulator (32-2) are sequentially connected, and control ports of the first external modulator (32-1) and the second external modulator (32-2) are respectively connected with the driving circuit (33);

the optical receiving unit (40) comprises a quasi-coherent special chip (41), a first local oscillation light input port, a second local oscillation light input port, a first optical coupler (43-1), a second optical coupler (43-2), a first polarization beam splitter (44-1), a second polarization beam splitter (44-2), a third optical detection unit, a fourth optical detection unit, a fifth optical detection unit and a sixth optical detection unit, wherein the first optical coupler (43-1) is connected with the first polarization beam splitter (44-1), the third optical detection unit and the fourth optical detection unit are respectively optically coupled with two paths of output light of the first polarization beam splitter (44-1), the second optical coupler (43-2) is connected with the second polarization beam splitter (44-2), and the fifth optical detection unit and the sixth optical detection unit are respectively coupled with two paths of output light of the second polarization beam splitter (44-2), the third optical detection unit, the fourth optical detection unit, the fifth optical detection unit and the sixth optical detection unit are respectively coupled with a group of ports of the quasi-coherent special chip (41);

the second port of the first optical splitter (34-1) is coupled with the second side of the first local oscillator optical input port, the first optical coupler (43-1) is coupled with the first side of the first local oscillator optical input port, the second port of the second optical splitter (34-2) is coupled with the second side of the second local oscillator optical input port, and the second optical coupler (43-2) is coupled with the first side of the second local oscillator optical input port.