CN113573176A

CN113573176A - ONU (optical network Unit), OLT (optical line terminal), optical communication system and data transmission method

Info

Publication number: CN113573176A
Application number: CN202010356197.8A
Authority: CN
Inventors: 周雷; 程远兵
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-04-29
Filing date: 2020-04-29
Publication date: 2021-10-29
Also published as: WO2021218181A1

Abstract

An optical network unit ONU, an optical line terminal OLT, an optical communication system and a data transmission method are used for solving the problem that the time delay of ONU for sending data is large in the prior art. The ONU can be applied to a passive optical network system and the like. The ONU can comprise an encoding module and an electro-optical conversion module; the encoding module is used for performing orthogonality encoding on data to be transmitted to obtain an electric signal and transmitting the electric signal to the electro-optical conversion module; the electro-optical conversion module is configured to convert the electrical signal into an optical signal, and send the optical signal to the optical line terminal OLT through the optical distribution network ODN. If a plurality of ONUs need to send data, the electric signals of the ONUs do not interfere with each other, and the data of the ONUs can simultaneously reach the OLT, thereby being beneficial to reducing the time delay of the data sent by the ONUs. Namely, through the orthogonal coding of the coding module, each ONU establishes a logical point-to-point link with the OLT.

Description

ONU (optical network Unit), OLT (optical line terminal), optical communication system and data transmission method

Technical Field

The present application relates to the field of communications technologies, and in particular, to an ONU, an OLT, an optical communication system, and a data transmission method.

Background

With the rapid development of broadband access technology, Passive Optical Network (PON) systems are increasingly applied in optical communication technology. The PON system includes an Optical Line Terminal (OLT) and a plurality of Optical Network Units (ONUs), where the OLT communicates with the ONUs. In the transmission of uplink signals, each ONU can only send data on the time slot allocated to itself, and the transmitter must be turned off in the rest of the time, so that if a plurality of ONUs transmit signals simultaneously, interference between the signals is caused.

In order to ensure the normal operation of a Time Division Multiplexing (TDM) PON, time slots for each ONU to transmit data need to be strictly allocated to avoid interference between signals. Moreover, the data of the ONUs different in time are not overlapped with each other from front to back, and a certain blank gap is left between each data in time, so as to further ensure that the time for sending the data is not overlapped. In this way, although crosstalk between signals can be avoided to some extent, data of an ONU arranged behind to transmit data obviously arrives at the OLT later than data of an ONU arranged in front, and particularly, when the number of ONUs arranged in front is large, the delay for transmitting data by the ONU behind is large.

Disclosure of Invention

The application provides an ONU, an OLT, an optical communication system and a data transmission method, which are used for reducing the time delay of data sent by the ONU.

In a first aspect, the present application provides an ONU comprising an encoding module and an electrical-to-optical conversion module; the encoding module is used for performing orthogonality encoding on data to be transmitted to obtain an electric signal and transmitting the electric signal to the electro-optical conversion module; the electro-optical conversion module is configured to convert the received electrical signal into an optical signal, and send the optical signal to the OLT through an Optical Distribution Network (ODN).

Based on the scheme, the coding module performs orthogonality coding on the data to be sent by the ONU to obtain electric signals, and the electric signals obtained by different ONUs are different and orthogonal to each other due to the orthogonality coding. If a plurality of ONUs need to send data, the electrical signals of the ONUs do not interfere with each other, and the ONUs can simultaneously transmit optical signals, that is, the data of the ONUs can overlap in time. In this way, data of multiple ONUs can simultaneously reach the OLT, which helps to reduce the delay of data sent by the ONUs. In addition, blank time slots do not need to be reserved between the ONUs in terms of time, and time delay of data sent by the ONUs can be further reduced. That is, through the orthogonal encoding of the encoding module, it is equivalent to that each ONU establishes a logical point-to-point link with the OLT (i.e. the ONU and the OLT are point-to-point independent transmission channels), and different links do not interfere with each other.

In one possible implementation, the encoding module is a Frequency Division Multiplexing Access (FDMA) encoder; the encoding module is specifically configured to determine a frequency band corresponding to the ONU, and perform multiplication on the data and the corresponding frequency band to obtain an electrical signal.

Through the FDMA encoder in the ONU, the orthogonality of electric signals of different ONUs on a frequency domain can be realized, so that the data transmitted by a plurality of ONUs simultaneously can be ensured not to interfere with each other.

Further, optionally, the encoding module is further configured to receive first configuration information from the OLT, where the first configuration information includes a frequency band corresponding to the ONU.

The OLT receives the first configuration information, so that the frequency band corresponding to the ONU can be quickly determined, and the coding efficiency of the coding module is improved.

In one possible implementation, the encoding module is a Code Division Multiple Access (CDMA) encoder; the encoding module is specifically configured to determine a codeword corresponding to the ONU, and perform multiplication on the data and the corresponding codeword to obtain an electrical signal.

By the CDMA encoder in the ONU, the orthogonality of electric signals of different ONUs in a time domain can be realized, so that data transmitted by a plurality of ONUs simultaneously are ensured not to interfere with each other.

Further, optionally, the encoding module is further configured to receive second configuration information from the OLT, where the second configuration information includes a codeword corresponding to the ONU.

And the OLT receives the second configuration information, so that the code word corresponding to the ONU can be quickly determined, and the coding efficiency of the coding module is improved.

In a possible implementation manner, the electro-optical conversion module is specifically configured to receive first injection light emitted by an injection light source from the OLT, generate a first optical carrier according to the first injection light, and modulate an electrical signal onto the first optical carrier to obtain an optical signal, where a wavelength of the first optical carrier is equal to a wavelength of the first injection light.

The first injection light received by the ONU and emitted from the injection light source of the OLT can control the wavelength of the optical signal emitted by the ONU, thereby contributing to reducing the complexity of data recovery of the OLT. Furthermore, the wavelengths of the first injection light received by each ONU are all equal, which can save wavelength resources, thereby contributing to reducing the cost of the integrated ONU.

In a possible implementation manner, the electro-optical conversion module is specifically configured to receive N second injection lights emitted by an injection light source from the OLT, generate a second optical carrier according to the N second injection lights, modulate an electrical signal onto the second optical carrier, and obtain an optical signal, where a wavelength of the second optical carrier is the same as a wavelength of one of the N second injection lights, and N is an integer greater than 1.

Through the ONU, the electro-optical conversion module receives the N second injection lights emitted by the injection light source from the OLT, so that the wavelength of an optical signal emitted by the ONU can be controlled, the complexity of recovering data by the OLT is reduced, and compared with the first injection light with a single wavelength, the N second injection lights with different wavelengths can further reduce the complexity of recovering data by the OLT.

In a second aspect, the present application provides an OLT comprising a photoelectric conversion module and a decoding module. The photoelectric conversion module is used for receiving the superposed optical signals through the ODN, converting the superposed optical signals into superposed electric signals and transmitting the superposed electric signals to the decoding module, wherein the superposed optical signals are obtained by superposing M optical signals from M ONUs (optical network units), the superposed electric signals comprise M mutually orthogonal electric signals, the M electric signals correspond to the M optical signals one by one, the M ONUs correspond to the M optical signals one by one, and M is an integer greater than 1; and the decoding module is used for decoding according to the superposed electric signals to obtain data sent by each ONU in the M ONUs.

Based on the scheme, the OLT receives the superposed optical signals, converts the superposed optical signals into superposed electric signals through the photoelectric conversion module, and decodes the superposed electric signals through the decoding module to simultaneously obtain M data from M ONUs. Thus, the time delay of the data transmitted by the M ONUs is reduced. Further, the superimposed electrical signals are M mutually orthogonal electrical signals, and do not interfere with each other, so that data sent by each ONU which is independent and does not interfere with each other can be obtained.

In one possible implementation, the decoding module is an FDMA decoder, and the FDMA decoder may include K filters, frequency bands allowed to pass by each of the K filters are different, and K is a positive integer; each filter in the K filters is used for allowing the electric signals of the corresponding frequency band in the superposed electric signals to pass through, one ONU corresponds to one frequency band, and the frequency bands corresponding to any two ONUs are not overlapped with each other.

Through the FDMA decoder in the OLT, the data sent by each ONU in the M ONUs can be decoded. In one possible implementation, the decoding module is a CDMA decoder; the CDMA decoder is used for performing multiplication and accumulation operation on the code word corresponding to each ONU in the M ONUs and the superposed electric signal to obtain data sent by each ONU in the M ONUs, wherein one ONU corresponds to one code word, and any two code words are orthogonal to each other.

And the data sent by each ONU in the M ONUs can be decoded by the CDMA decoder in the OLT.

In one possible implementation, the OLT may further include an injection light source; the injection light source is used for respectively emitting first injection light to each ONU in the M ONUs; the first injected light is used for the ONU to generate a first optical carrier, the first optical carrier is used for bearing an electric signal of the ONU, and the wavelength of the first optical carrier is the same as that of the first injected light.

Through the injection light source in the OLT, the first injection light with a single wavelength can be emitted to each ONU in the M ONUs, so that the wavelength of the optical signal emitted by the ONU can be equal to the wavelength of the first injection light, that is, the wavelength of the optical signal emitted by the ONU can be controlled, and the complexity of recovering the data of the ONU by the OLT can be reduced.

In a possible implementation manner, the OLT further includes an injection light source, where the injection light source is configured to respectively emit N second injection lights to each of the M ONUs; the N second injection lights are used for the ONU to generate a second optical carrier, the second optical carrier is used for carrying an electrical signal of the ONU, the N second injection lights have different wavelengths, the wavelength of the second optical carrier is the same as the wavelength of one of the N second injection lights, and N is an integer greater than 1.

Through the injection light source in the OLT, N second injection lights can be emitted to each ONU of the M ONUs, so that the ONU can select one second injection light with one wavelength from the N second injection lights, and the wavelength of an optical signal emitted by the ONU is the same as that of the selected second injection light, so that the wavelength of the optical signal emitted by the ONU is controllable, thereby contributing to reducing the complexity of the OLT in recovering data of the ONU.

In one possible implementation, the photoelectric conversion module is a coherent receiver, and the coherent receiver includes an intrinsic light source, an optical mixer, and a balanced detector; the intrinsic light source is used for emitting intrinsic light to the optical mixer; the optical mixer is used for carrying out frequency mixing processing on the received intrinsic light and the superposed light signal to obtain a frequency mixing signal and transmitting the frequency mixing signal to the balance detector; the balance detector is used for converting the mixing signal into a superposed electric signal and transmitting the superposed electric signal to the decoding module.

The received superimposed optical signal can be converted into a superimposed electrical signal by the coherent receiver in the OLT. Also, it contributes to improvement of the reception performance.

In one possible implementation, the photoelectric conversion module may include an Avalanche Photodiode (APD) and a trans-impedance amplifier (TIA); the APD is used for receiving the superposed optical signals and converting the superposed optical signals into superposed current signals; the TIA is used for converting the superposed current signal into a superposed voltage signal.

The received superimposed optical signal can be converted into a superimposed electrical signal by the APD and TIA in the OLT. Furthermore, the APD has a gain of 10-200 times, and the sensitivity of receiving the superposed optical signals can be improved. Moreover, since the superposed electrical signals are M electrical signals which are different from each other and orthogonal to each other, the TIA does not need a burst TIA, that is, the TIA does not need to perform a rapid amplification factor switching function, and can directly multiplex the TIA in the prior art, which is helpful for reducing the cost of the integrated OLT.

In one possible implementation, the superimposed electrical signals include superimposed analog electrical signals and superimposed digital electrical signals; the OLT also comprises an analog-digital conversion module; the analog-to-digital conversion module is used for receiving the superposed analog electric signal from the photoelectric conversion module, converting the superposed analog electric signal into a superposed digital electric signal and transmitting the superposed digital electric signal to the decoding module.

In a third aspect, the present application provides an optical communication system, which may include M ONUs of any one of the first aspect or the first aspect, an OLT of any one of the second aspect or the second aspect, and an ODN, where the OLT communicates with each ONU of the M ONUs through the ODN.

Based on the optical communication system, the encoding module in the ONU performs orthogonality encoding on data to be transmitted by the ONU to obtain electrical signals, and because the data are orthogonality encoding, the electrical signals obtained by different ONUs are different and orthogonal to each other. If a plurality of ONUs need to send data, the electrical signals of the ONUs do not interfere with each other, and the ONUs can simultaneously transmit optical signals to the OLT, that is, the data of the ONUs can overlap in time. In this way, data of multiple ONUs can simultaneously reach the OLT, which helps to reduce the delay of data sent by the ONUs. That is, through the orthogonal encoding of the encoding module, it is equivalent to that each ONU establishes a logical point-to-point link with the OLT (i.e. the ONU and the OLT are point-to-point independent transmission channels), and different links do not interfere with each other. The superposed electric signals are decoded by the decoding module, so that M data from M ONUs can be obtained simultaneously.

In one possible implementation manner, the ODN includes a trunk optical fiber, an optical splitter and M branch optical fibers, the M branch optical fibers correspond to the M ONUs one to one, the optical splitter is connected to each ONU of the M ONUs through a corresponding branch optical fiber, the OLT is connected to the optical splitter through the trunk optical fiber, and M is an integer greater than 1; each ONU in the M ONUs is used for sending an optical signal to the optical splitter through a corresponding branch optical fiber; the optical splitter is used for combining the received M optical signals to obtain superposed optical signals, and sending the superposed optical signals to the OLT through the trunk optical fiber.

In a fourth aspect, the present application provides a data transmission method, which is applicable to the ONU of any one of the first aspect or the first aspect. The method can include that orthogonality coding is carried out on data to be transmitted to obtain an electric signal; converts the electrical signal to an optical signal and transmits the optical signal to the OLT through the ODN.

The following exemplary shows two implementations of orthogonalizing the data to be transmitted.

In implementation mode 1, the frequency band corresponding to the ONU is determined, and the data and the corresponding frequency band are multiplied to obtain an electrical signal. It should be understood that different ONUs correspond to different frequency bands, and the frequency bands corresponding to any two ONUs do not overlap.

Further, optionally, first configuration information from the OLT may be received, where the first configuration information includes a frequency band corresponding to the ONU.

In implementation mode 2, the code word corresponding to the ONU is determined, and the data and the corresponding code word are multiplied to obtain an electrical signal. It should be understood that different ONUs correspond to different code words, and that different code words are orthogonal to each other.

Further, optionally, second configuration information may be received from the OLT, where the second configuration information includes a codeword corresponding to the ONU.

In a possible implementation manner, a first injected light emitted from the OLT may be received, a first optical carrier may be generated according to the first injected light, and an electrical signal may be modulated onto the first optical carrier to obtain an optical signal, where a wavelength of the first optical carrier is equal to a wavelength of the first injected light.

In another possible implementation manner, N second injection lights emitted from the OLT may be received, a second optical carrier may be generated according to the N second injection lights, and an electrical signal is modulated onto the second optical carrier to obtain an optical signal, where a wavelength of the second optical carrier is the same as a wavelength of one of the N second injection lights, and N is an integer greater than 1;

for technical effects that can be achieved by any aspect of the fourth aspect, reference may be made to the description of the advantageous effects in the first aspect, and details are not repeated here.

In a fifth aspect, the present application provides a data transmission method, which is applicable to the OLT of any one of the second aspect or the second aspect. The method can include receiving superimposed optical signals through an Optical Distribution Network (ODN), and converting the superimposed optical signals into superimposed electrical signals, wherein the superimposed optical signals are obtained by superimposing M optical signals from M Optical Network Units (ONU), the superimposed electrical signals include M mutually orthogonal electrical signals, the M electrical signals correspond to the M optical signals one by one, the M ONU corresponds to the M optical signals one by one, and M is an integer greater than 1; and decoding according to the superposed electric signals to obtain data sent by each ONU in the M ONUs.

The following exemplarily shows two implementations of decoding.

In the implementation mode a, the electric signals of the corresponding frequency bands in the superimposed electric signals are allowed to pass through respectively, so as to obtain data sent by each ONU in the M ONUs, where one ONU corresponds to one frequency band, and the frequency bands corresponding to any two ONUs do not overlap with each other.

In the implementation mode B, the data sent by each ONU is obtained by performing multiply-accumulate operation on the code word corresponding to each ONU in the M ONUs and the superposed electric signal, wherein one ONU corresponds to one code word, and any two code words are orthogonal to each other.

In a possible implementation manner, the method further includes respectively emitting a first injection light to each ONU of the M ONUs, where the first injection light is used for the ONU to generate a first optical carrier, the first optical carrier is used to carry an electrical signal of the ONU, and a wavelength of the first optical carrier is the same as a wavelength of the first injection light.

In one possible implementation, the method further includes respectively emitting N second injection lights to each of the M ONUs; the N second injection lights are used for the ONU to generate a second optical carrier, the second optical carrier is used for carrying an electrical signal of the ONU, the N second injection lights have different wavelengths, the wavelength of the second optical carrier is the same as the wavelength of one of the N second injection lights, and N is an integer greater than 1.

In a possible implementation manner, the method may further include receiving the intrinsic light, and performing frequency mixing processing on the intrinsic light and the superimposed light signal to obtain a frequency mixing signal; the mixed signal is converted into a superimposed electrical signal.

In another possible implementation, the method may include converting the superimposed optical signal to a superimposed current signal, and converting the superimposed current signal to a superimposed voltage signal.

In one possible implementation, the superimposed electrical signals include superimposed analog electrical signals and superimposed digital electrical signals; the method may further include receiving the superimposed analog electrical signal from the photoelectric conversion module and converting the superimposed analog electrical signal to a superimposed digital electrical signal.

The technical effect that can be achieved by any aspect of the fifth aspect may refer to the description of the beneficial effect in the second aspect, and details are not repeated here.

Drawings

Fig. 1 is a schematic diagram of a PON system architecture provided in the present application;

fig. 2 is a schematic diagram of uplink transmission provided in the present application;

fig. 3 is a schematic structural diagram of an ONU provided in the present application;

fig. 4a is a schematic diagram of an FDMA codec provided in the present application;

fig. 4b is a schematic diagram of a CDMA codec provided in the present application;

fig. 5a is a schematic diagram illustrating a principle of injecting light to lock an ONU emission wavelength according to the present application;

fig. 5b is a schematic diagram of another principle of injecting light to lock an ONU emitting wavelength provided by the present application;

fig. 6 is a schematic structural diagram of an OLT according to the present application;

fig. 7a is a schematic structural diagram of a coherent receiver provided in the present application;

fig. 7b is a schematic structural diagram of a photoelectric conversion module provided in the present application;

fig. 8 is a schematic diagram of an optical communication system architecture provided in the present application;

fig. 9a is a schematic diagram of a PON system architecture according to the present application;

fig. 9b is a schematic diagram of another PON system architecture provided in the present application;

fig. 10 is a schematic flowchart of a method of data transmission provided in the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings.

Hereinafter, some terms in the present application are explained to facilitate understanding by those skilled in the art.

Passive Optical Network (PON)

The PON does not include any electronic device and electronic power supply in an Optical Distribution Network (ODN), and the ODN is composed of passive devices such as a splitter (splitter), and does not require active electronic devices. And are therefore referred to as passive optical networks. Generally, a passive optical network includes an Optical Line Terminal (OLT) installed at a central control station and a plurality of Optical Network Units (ONUs) installed at customer sites in a coordinated manner.

Two, coherent detection

Coherent detection may also be referred to as optical heterodyne detection. Coherent detection is based on the principle that coherent intrinsic light (or referred to as reference light) and incident signal light are mixed on a photosurface. The coherent intrinsic light and the coherent signal light mean that the frequency of the intrinsic light is very close to the frequency of the signal light, so that the intrinsic light and the signal light can form a beat frequency signal on a photosensitive surface of the photoelectric detector.

Frequency Division Multiplexing Access (FDMA)

FDMA divides the total bandwidth into multiple orthogonal channels, each user occupying a channel (carrier) of one frequency, which can be used simultaneously in time. That is, different users occupy different frequencies, i.e., different users employ different carrier frequencies. At the receiving end, the corresponding filters can be used to distinguish (or select) each path of signal, and then each path of original signal can be recovered through the respective decoder.

Code Division Multiple Access (CDMA)

CDMA is a method for implementing multiple access communication by using orthogonality of address codes, and each transmitting end modulates signals transmitted by the transmitting end by using the mutually orthogonal address codes. At the receiving end, the orthogonality of the address codes is used, and the corresponding signals are selected from the mixed signals (or called superposed signals) through address identification. CDMA systems assign one or more address codes (or called codewords) to each user. The address codes of the users are different from each other and are orthogonal to each other.

Based on the above, as shown in fig. 1, a schematic diagram of a PON system architecture provided by the present application is shown. The PON system is a multi-point to point (MP 2P) system based on a tree network topology structure, the PON system is illustrated as including an OLT, three ONUs (or optical network terminals, ONTs), and an ODN, the OLT is connected to each of the three ONUs via the ODN, the three ONUs in FIG. 1 are ONU1, ONU2, and ONU3, respectively; the ODN comprises a trunk optical fiber, a splitter (splitter), which may also be referred to as an optical splitter, which may be a fiber tandem having a plurality of inputs and a plurality of outputs, and is mainly used for coupling and distributing optical signals, the OLT is connected to the splitter via the trunk optical fiber, and the splitter is connected to each ONU via a branch optical fiber, it being understood that the OLT is a central office device, the ONUs are end devices, in addition, the number of the OLTs and ONUs included in the PON system is not limited in the present application.

The transmission direction of the optical signal from the OLT to the ONU is referred to as a downstream direction. The direction in which optical signals are transmitted from the ONUs to the OLT is referred to as the upstream direction. The OLT may transmit the optical signal to the ONU in a broadcast manner, and the ONU may transmit the optical signal to the OLT in a unicast manner. It should be understood that for the upstream direction, the PON system is an MP2P system; for the downstream direction, the PON system is a point-to-multipoint (P2 multiple point, P2MP) system.

At present, time division multiplexing access is generally adopted for uplink transmission (i.e. transmission direction from ONU to OLT). Such as Time Division Multiple Access (TDMA). In one possible implementation, with reference to fig. 1, after the OLT measures the distance between the OLT itself and each ONU, the OLT performs strict transmission timing for each ONU, and the ONU acquires timing information from a downstream signal transmitted by the OLT and transmits an upstream signal in a time slot defined by the OLT.

Referring to fig. 2, each Dynamic Bandwidth Allocation (DBA) period (uplink transmission time) is divided into a plurality of time slots Ti (i ═ 1,2,3, … … 32, … …), only one ONU is arranged (or allocated) to transmit an uplink optical signal to the OLT in each time slot, and each ONU sequentially transmits optical signals in the order of the time slots allocated by the OLT. It should be noted that one ONU may be allocated one or more time slots.

Because the ONU transmits (in the uplink direction) data to the OLT by using the time division multiplexing technique, if a plurality of ONUs transmit optical signals simultaneously, the optical signals of the ONUs interfere with each other, so that the OLT cannot normally receive the data of the ONUs, and further, the service of the entire PON network is interrupted. In order to avoid interference between the optical signals of the ONUs as much as possible, each ONU is required to transmit the optical signal only when its own time slot arrives, and cannot transmit the optical signal for the rest of the time. Therefore, data of the ONU arranged behind the ONU for transmitting data obviously arrives at the OLT later than data of the ONU arranged in front of the ONU, and especially, when the number of the ONU arranged in front is large, the delay of the data transmitted by the ONU arranged behind the ONU is larger. Moreover, the optical signal sent by the ONU to the OLT generally needs to carry a part of overhead data, for example, a signal used for clock synchronization by the OLT, signal interaction (for example, bandwidth request information reported by the ONU to the OLT, operating temperature information, and the like), and bandwidth waste is caused. It should be understood that a mode in which an ONU can transmit an optical signal only when its own time slot arrives is called "burst transmission mode", an optical signal that an ONU transmits in its own time slot is called "burst packet", and an ONU that does not transmit at will in its own time slot is called a rogue ONU.

In view of the above problems, the present application proposes an ONU, an OLT, and an optical communication network. The ONU proposed in the present application is specifically described below with reference to fig. 3, fig. 4a, fig. 4b, fig. 5a, and fig. 5 b; the OLT proposed in the present application is specifically explained with reference to fig. 6, fig. 4a, fig. 4b, fig. 7a, and fig. 7 b; the optical communication system proposed in the present application will be specifically explained with reference to fig. 8, fig. 9a and fig. 9 b.

Based on the above, as shown in fig. 3, a schematic structural diagram of an ONU provided by the present application is shown. The ONU may include an encoding module and an electrical-to-optical conversion module. The encoding module is used for performing orthogonality encoding on data to be transmitted to obtain an electric signal and transmitting the electric signal to the electro-optical conversion module; the electro-optical conversion module is used for converting the received electric signal into an optical signal and sending the optical signal to the OLT through the ODN.

It should be noted that the data to be sent refers to valid data to be sent by the ONU, such as voice information of a user or internet access information of the user, and overhead data does not exist, so that the uplink bandwidth utilization rate is high. The electrical signals obtained by orthogonal coding of the data to be transmitted are the coded data, and the coded data obtained by different ONUs are different and mutually orthogonal, that is, the electrical signals obtained by different ONUs are different and mutually orthogonal.

Based on the ONU, the coding module performs orthogonality coding on data to be sent by the ONU to obtain electric signals, and the electric signals obtained by different ONUs are different and orthogonal to each other due to the orthogonality coding. If a plurality of ONUs need to send data, the electrical signals of the ONUs do not interfere with each other, and the ONUs can simultaneously transmit optical signals, that is, the data of the ONUs can overlap in time. In this way, data of multiple ONUs can simultaneously reach the OLT, which helps to reduce the delay of data sent by the ONUs. In addition, blank time slots do not need to be reserved between the ONUs in terms of time, and time delay of data sent by the ONUs can be further reduced. That is, through the orthogonal encoding of the encoding module, it is equivalent to that each ONU establishes a logical point-to-point link with the OLT (i.e. the ONU and the OLT are point-to-point independent transmission channels), and different links do not interfere with each other. Furthermore, each ONU transmits effective data without transmitting overhead data, thereby being beneficial to saving bandwidth.

The functional blocks shown in fig. 3 are described separately below to give an exemplary specific implementation.

Coding module

In one possible implementation, the encoding module may be an FDMA encoder or may also be a CDMA encoder. The FDMA coder refers to a coder adopting FDMA coding, and the FDMA coding has orthogonality of a frequency domain; a CDMA encoder refers to an encoder that employs CDMA coding, which has orthogonality in the time domain. That is, the orthogonal codes can be implemented by CDMA coding or FDMA coding, so that it can be ensured that data transmitted by a plurality of ONUs do not interfere with each other.

As follows, the coding module is an FDMA coder or a CDMA coder for example, and will be described in detail respectively.

Case one, the encoding module is an FDMA encoder.

In a possible implementation manner, each ONU may correspond to one frequency band, and further, the FDMA encoder may determine the frequency band corresponding to the ONU, and perform multiplication operation on data to be transmitted and the corresponding frequency band to obtain an electrical signal.

In a possible implementation manner, the frequency band corresponding to the ONU may be: the ONU receives first configuration information from the OLT, wherein the first configuration information comprises a frequency band corresponding to the ONU; or, the ONU and the OLT are agreed in advance; alternatively, the ONU stores the frequency band corresponding to the ONU locally in advance, or may be specified by a protocol, which is not limited in the present application. In addition, the frequency bands corresponding to any two ONUs are not overlapped.

With reference to fig. 1, as shown in fig. 4a, a schematic diagram of an FDMA codec provided by the present application is shown. In fig. 4a, ONU1 corresponds to frequency band 1, ONU2 corresponds to frequency band 2, ONU3 corresponds to frequency band 3, data to be transmitted by ONU1 is data 1, data to be transmitted by ONU2 is data 2, and data to be transmitted by ONU3 is data 3; an encoding module in the ONU1 is an FDMA encoder 1, an encoding module in the ONU2 is an FDMA encoder 2, and an encoding module in the ONU3 is an FDMA encoder 3; the FDMA encoder 1 is configured to multiply the data 1 with the corresponding frequency band 1 to obtain an electrical signal 1 (denoted by TX 1); the FDMA encoder 2 is configured to multiply the data 2 by the corresponding frequency band 2 to obtain an electrical signal 2 (denoted by TX 2); FDMA encoder 3 is configured to multiply data 3 by band 3 to obtain an electrical signal 3 (denoted by TX 3). It should be understood that the frequency band may be represented by a sine wave, and the frequency bands occupied by any two ONUs do not overlap with each other. In addition, since the intermediate frequency is generally used as a transmission frequency or a reception frequency, the intermediate frequency may be selected for a frequency band corresponding to the ONU. It should be noted that the electrical signal 1 is the encoded data 1, the electrical signal 2 is the encoded data 2, and the electrical signal 3 is the encoded data 3.

In case two, the encoding module is a CDMA encoder.

In one possible implementation, the CDMA encoder may implement orthogonality in the time domain via orthogonal codes (codes). The corresponding code words of the ONUs are different and orthogonal to each other. Illustratively, the codewords are code1 ═ {1,1,1,1}, code2 ═ {1, -1,1, -1}, code3 ═ {1,1, -1, -1}, respectively, and code1, code2, and code3 are different from each other and orthogonal to each other. It should be noted that the code word includes, but is not limited to, 4 bits.

In a possible implementation manner, the ONU may determine a codeword corresponding to the ONU, and perform multiplication on the data and the corresponding codeword to obtain an electrical signal. Further, optionally, the code word corresponding to the ONU may be: the ONU receives second configuration information from the OLT, wherein the second configuration information comprises a code word corresponding to the ONU; or, the ONU and the OLT are agreed in advance; alternatively, the ONU stores the code word corresponding to the ONU locally in advance, or may be specified by a protocol, which is not limited in this application.

With reference to fig. 1, as shown in fig. 4b, a schematic diagram of a CDMA codec provided in the present application is shown. In fig. 4b, for example, ONU1 corresponds to code word code1 ═ {1,1,1,1}, ONU2 corresponds to code word code2 ═ {1, -1,1, -1}, and ONU3 corresponds to code word code3 ═ {1,1, -1, -1 }. The data to be sent of ONU1 is data 1, the data to be sent of ONU2 is data 2, and the data to be sent of ONU3 is ONU 3; an encoding module in the ONU1 is a CDMA encoder 1, an encoding module in the ONU2 is a CDMA encoder 2, and an encoding module in the ONU3 is a CDMA encoder 3; the CDMA encoder 1 multiplies the data 1 by the code1 to obtain an electrical signal 1, TX1 being data 1 × (1+1+1+ 1); the CDMA encoder 2 is configured to multiply the data 2 by the code2 to obtain an electrical signal 2, where TX2 is data 2 (1-1+ 1-1); the CDMA encoder 3 multiplies the data 3 by the code3 to obtain an electrical signal 3, TX3 being data 3 × (1+ 1-1-1). It should be understood that the electrical signal 1 is the encoded data 1, the electrical signal 2 is the encoded data 2, and the electrical signal 3 is the encoded data 3.

The CDMA encoder or the FDMA encoder can realize that the data to be sent of different ONUs are subjected to orthogonality processing to obtain different and mutually orthogonal electric signals, so that a plurality of ONUs can send optical signals to an OLT at the same time and do not interfere with one another.

Two, electro-optical conversion module

In this application, the electro-optical conversion module may be configured to convert the received electrical signal into an optical signal, and send the optical signal to the OLT through the ODN.

In one possible implementation, the electro-optical conversion module may be a Distributed Feedback (DFB) laser, a Fabry-Perot (FP) laser, an electro-absorption modulated laser (EML), or the like. The FP laser, the DFB laser and the EML are all wavelength tunable lasers, and the wavelength tunable lasers refer to lasers with the output laser wavelength capable of being changed according to needs. The details are described below.

The DFB laser mainly uses semiconductor materials as media, including gallium antimonide (GaSb), gallium arsenide (GaAs), indium phosphide (InP), zinc sulfide (ZnS), and has a high side-mode suppression ratio (SMSR), where SMSR is a ratio of a main mode intensity to a maximum value of a side mode intensity, and is an important index for marking a longitudinal mode performance. A grating is integrated in the active layer of the DFB laser, i.e. the laser oscillation of the DFB laser is optically coupled by the grating. The wavelength to be output by the DFB laser can be adjusted by changing the current injected into the DFB laser until the wavelength to be output by the DFB laser is equal to the wavelength of the injected light received by the DFB laser, and the DFB laser outputs the optical signal with the wavelength as an output optical signal. That is, the DFB laser receives the injected light and can emit light of the same wavelength as the injected light, and therefore, is also referred to as being injection-locked.

The principle of EML output optical signals is the same as that of DFB lasers described above. The wavelength to be output by the EML can be adjusted by changing the current injected into the EML until the wavelength to be output by the EML is equal to the wavelength of the injected light received by the EML, and the EML outputs the optical signal with the wavelength as an output optical signal.

The principle of output optical signals of the FP laser is as follows: the injected light is injected into the optical resonant cavity of the FP laser, and the lasing wavelength of the optical resonant cavity of the FP laser can be forced to be consistent with the wavelength of the injected light.

In a possible implementation manner, the electro-optical conversion module may be configured to receive a first injection light emitted by an injection light source from the OLT, generate a first optical carrier according to the first injection light, and modulate an electrical signal onto the first optical carrier to obtain an optical signal, where a wavelength of the first optical carrier is equal to a wavelength of the first injection light. Referring to fig. 5a in conjunction with fig. 1, if all of the wavelengths of the first injection light emitted from the injection light source of the OLT are λ received by ONU1, ONU2, and ONU3₁And the wavelength of the first optical carrier generated by the ONU1 is λ₁The wavelength of the first optical carrier generated by the ONU2 is also λ₁The wavelength of the first optical carrier generated by the ONU3 is also λ₁. For the description of the injection light source of the OLT, reference may be made to the following description of the injection light source, and details are not repeated here.

In another possible implementation manner, the electro-optical conversion module may be configured to receive N second injection lights emitted by an injection light source from the OLT, generate a second optical carrier according to the N second injection lights, and modulate an electrical signal onto the second optical carrier to obtain an optical signal, where a wavelength of the second optical carrier is the same as a wavelength of one of the N second injection lights, and N is an integer greater than 1. It should be understood that the number N of second injection light emitted by the OLT is greater than or equal to the number of ONUs in the optical communication system in which the ONUs are located.

Further, optionally, the electro-optical conversion module may be further configured to receive indication information from the OLT, where the indication information is used to indicate which wavelength of the second injected light is selected by the electro-optical conversion module, that is, the wavelength of the generated second optical carrier needs to be the same as the wavelength of which second injected light. Alternatively, it can also be understood that the OLT assigns a wavelength of the second injection light to the ONU, and the ONU tunes the wavelength to this assigned wavelength.

Referring to fig. 5b in conjunction with fig. 1, if ONU1, ONU2, and ONU3 receive 3 second injection lights emitted from the injection light source of the OLT, the wavelengths of the two injection lights are λ₁、λ₂And λ₃The wavelength of the second optical carrier generated by the ONU1 may be λ₁The wavelength of the second optical carrier generated by the ONU2 is also λ₂The wavelength of the second optical carrier generated by the ONU3 is also λ₃. Of course, the wavelength of the second optical carrier generated by the ONU1 may be λ₂The wavelength of the second optical carrier generated by the ONU2 is also λ₃The wavelength of the second optical carrier generated by the ONU3 is also λ₁(ii) a Alternatively, the second optical carrier generated by the ONU1 may have a wavelength λ₃The wavelength of the second optical carrier generated by the ONU2 is also λ₁The wavelength of the second optical carrier generated by the ONU3 is also λ₂Etc., fig. 5b is only an example, and the wavelength of the second optical carrier generated by the ONU may be determined according to the indication information from the OLT, or it may be understood that the OLT allocates the second injection light of one wavelength to the ONU, and the ONU tunes the wavelength to the allocated wavelength. For the description of the injection light source of the OLT, reference may be made to the following description of the injection light source, and details are not repeated here.

In yet another possible implementation manner, the electrical-to-optical conversion module may also randomly generate a third optical carrier wave with one wavelength; or the electro-optical conversion module adjusts and generates a third optical carrier with a wavelength by itself, and modulates the electric signal to the third optical carrier to obtain an optical signal.

Fig. 6 is a schematic structural diagram of an OLT according to the present application. The OLT comprises a photoelectric conversion module and a decoding module; the optical-electrical conversion module is used for receiving the superposed optical signals through the ODN, converting the superposed optical signals into superposed electrical signals and transmitting the superposed electrical signals to the decoding module, wherein the superposed optical signals are obtained by superposing M optical signals from M Optical Network Units (ONU), the superposed electrical signals comprise M mutually orthogonal electrical signals, the M electrical signals correspond to the M optical signals one by one, the M ONU corresponds to the M optical signals one by one, and M is an integer greater than 1; and the decoding module is used for decoding according to the superposed electric signals to obtain data sent by each ONU in the M ONUs.

The superimposed optical signal is obtained by superimposing the powers of the M optical signals. With reference to fig. 1, for example, the power of ONU1 is 1mW, the power of ONU2 is 1mW, the power of ONU3 is 1mW, and the superimposed power is 1+1+1 — 3 mW. The superimposed electrical signal is obtained by superimposing M electrical signals, for example, electrical signal 1 is represented by TX1, electrical signal 2 is represented by TX2, electrical signal 3 is represented by TX3, and electrical signal 1, electrical signal 2, and electrical signal 3 are superimposed to obtain a superimposed electrical signal TX ═ TX1+ TX2+ TX3, where electrical signal 1, electrical signal 2, and electrical signal 3 are different and orthogonal to each other.

Based on the OLT, the OLT receives the superposed optical signals, converts the superposed optical signals into superposed electrical signals through the photoelectric conversion module, and decodes the superposed electrical signals through the decoding module to simultaneously obtain M data from M ONUs. Thus, the time delay of the data transmitted by the M ONUs is reduced. Further, the superimposed electrical signals are M mutually orthogonal electrical signals, and do not interfere with each other, so that data sent by each ONU which is independent and does not interfere with each other can be obtained.

The functional blocks shown in fig. 6 are described separately below to give an exemplary specific implementation.

Third, photoelectric conversion module

In the present application, the photoelectric conversion module is used to convert a superimposed optical signal into a superimposed electrical signal, and the structures of the two photoelectric conversion modules are exemplarily shown as follows.

In the first structure, the photoelectric conversion module is a coherent receiver.

Fig. 7a is a schematic structural diagram of a coherent receiver according to the present application. The coherent receiver includes an intrinsic light source, an optical mixer, and a balanced detector. The intrinsic light source is used for emitting intrinsic light to the optical mixer. The optical mixer is used for carrying out frequency mixing processing on the received intrinsic light and the superposed light signal to obtain a frequency mixing signal, and transmitting the frequency mixing signal to the balance detector. That is, the mixer inputs the intrinsic light at one end and the superimposed optical signal at the other end. In one possible implementation, the frequency of the mixing signal output by the mixer is equal to the sum, sum and difference of the frequencies of the two input signals. Mixers are commonly used to generate intermediate frequency signals: cos α cos β ═ cos (α + β) + cos (α - β) ]/2, cos α and cos β are the two signals input (e.g., the superimposed optical signal and the intrinsic light), and cos (α + β) and cos (α - β) are the mixed signals output. The balance detector is used for converting the mixing signal into a superposed electric signal and transmitting the superposed electric signal to the decoding module. Further, optionally, the balanced detector may comprise a Photo Diode (PD) and a TIA.

And in a second structure, the photoelectric conversion module comprises an APD and a TIA.

Fig. 7b is a schematic structural diagram of a photoelectric conversion module provided in the present application. The photoelectric conversion module may include an APD and a TIA. The APD is used for receiving the superposed optical signals and converting the superposed optical signals into superposed current signals; the TIA is used for converting the received superposed current signal into a superposed voltage signal.

The APD converts a received superimposed optical signal into a superimposed current signal based on the principle of the photoelectric effect. Moreover, the APD has 10-200 times of gain, and the sensitivity of receiving the superposed optical signals can be improved. In the prior art, the electric power of the burst packets is different, and the OLT needs to have uniform power of the electric signal, so the TIA device in the prior art needs to have a function of switching the amplification factor quickly. Namely, when the burst packet is high, the amplification factor is switched to be low; and switching to high amplification when the burst packet is in low power. However, in the present application, since the superimposed electrical signals are M electrical signals that are different from each other and are orthogonal to each other, a burst TIA is not required, that is, the TIA does not need to perform a fast amplification factor switching function, and can directly multiplex the TIA in the prior art, and therefore, the cost of the integrated OLT is low.

Four, decoding module

In one possible implementation, the decoding module may be an FDMA decoder or may also be a CDMA decoder. The data from each ONU is coded by the FDMA coder of the ONU to obtain the coded data, and the coded data of each ONU occupies different frequency bands, so that the data of each ONU which are independent and do not interfere with each other can be obtained after the data is filtered by the FDMA decoder. And after the data from each ONU is coded by the CDMA coder of the ONU, the coded data is obtained, the multiply-accumulate operation of the coded data of each ONU and the corresponding code word is not equal to zero, and the multiply-accumulate operation of the coded data of each ONU and other code words is equal to zero.

In a possible implementation manner, the FDMA decoder may include K filters, where frequency bands allowed to pass through by each of the K filters are different, each of the K filters is configured to allow an electrical signal in a corresponding frequency band in the superimposed electrical signal to pass through, one ONU corresponds to one frequency band, frequency bands corresponding to any two ONUs do not overlap with each other, and K is a positive integer. Because the data of each ONU occupies different frequency bands, the independent and non-interfering data of each ONU can be obtained after the data is filtered by the corresponding filter.

It should be noted that K is usually equal to M, i.e. one ONU corresponds to one filter. K may also be smaller than M, i.e. multiple ONUs correspond to one filter. For example, two ONUs correspond to one filter, and the filter may allow frequency bands corresponding to the two ONUs to pass through. Of course, K may be larger than M, and one ONU corresponds to one filter, that is, a part of the filter is used for corresponding to the newly added ONU when the ONU is newly added.

Based on the above situation one, referring to fig. 4a, the superimposed electrical signal received by the FDMA decoder is RX, TX, 1+ TX2+ TX3, the filter 1 allows the electrical signal 1 in the frequency band 1 to pass through, the filter 2 allows the electrical signal 2 in the frequency band 2 to pass through, and the filter 3 allows the electrical signal 3 in the frequency band 3 to pass through. That is, when the superimposed electrical signal RX passes through the filter 1, the electrical signal 1 is obtained; when passing through the filter 2, an electric signal 2 can be obtained; when passing through the filter 3, an electrical signal 3 is obtained.

Further, optionally, since the frequency band corresponding to the ONU is usually an intermediate frequency, but decoding and recovering the electrical signal are performed at a low frequency band, in order to rapidly recover the data of each ONU, the FDMA decoder may further include K down-converters, where the K down-converters are in one-to-one correspondence with the K filters, and each of the K down-converters is configured to convert the corresponding electrical signal into an electrical signal (e.g., a baseband signal) at the low frequency band. Illustratively, the down converter 1 may convert the electrical signal 1 into an electrical signal 1 of a low frequency band, the down converter 2 may convert the electrical signal 2 into an electrical signal 2 of a low frequency band, and the down converter 3 may convert the electrical signal 2 into an electrical signal 3 of a low frequency band, wherein the electrical signal 1 of a low frequency band, the electrical signal 2 of a low frequency band, and the electrical signal 3 of a low frequency band may all be baseband signals.

Based on the second case, referring to fig. 4b, the CDMA decoder receives the superimposed electrical signal RX, RX TX (TX 1+ TX2+ TX 3) (data 1 (1+1+1+1) + data 2 (1-1+1-1) + data 3 (1+ 1-1-1-1). The process of the CDMA decoder to decode data 1 of ONU1 may be: the ONU1 for the CDMA decoder performs multiply-accumulate operation on the code word code1 and the superimposed electrical signal RX, that is: RX ═ code1 ═ data 1 × (1+1+1+1) + data 2 × (1-1+1-1) + data 3 × (1+1-1-1) ] (1+1+ 1) ═ data 1 × (1+1+1+1) × (1+1+ 1) + data 2 (1-1+1-1) ((1 +1+1+1) + data 3 (1+1-1-1) ((1 +1+1) + data 1 ═ data (1+1+1+1) + data 2 × (1-1-1) ═ data 1+0+ 4 ═ data 1. Due to the orthogonality of the orthogonal codes, ONU2 and ONU3 decode to be equal to 0, and only decode data 1 of ONU 1.

The process of the CDMA decoder to decode data 2 of ONU2 is: the CDMA decoder multiplies and accumulates the code word code2 corresponding to the ONU2 with the superimposed electrical signal RX, that is: RX ═ code2 ═ data 1 × (1+1+ 1) + data 2 × (1-1+1-1) + data 3 × (1+1-1-1) ] (1-1+1-1) ═ data 1 × (1+1+1+1) × (1-1+1-1) + data 2: (1-1+1-1) (1-1+1-1) + data 3 (1+1-1-1) ((1-1 +1) × (1-1+ 1) + data 2 ═ 1+1) ((0 +4 ═ data 2+ 4 ═ data. Due to the orthogonality of the orthogonal codes, ONU1 and ONU3 decode to be equal to 0, and only decode data 2 of ONU 2.

The process of decoding the data of the ONU3 by the CDMA decoder is: the CDMA decoder multiplies and accumulates the code word code3 corresponding to the ONU3 with RX, that is: RX ═ code3 ═ data 1 × (1+1+ 1) + data 2 × (1-1+1-1) + data 3 × (1+1-1-1) ] (1+1-1-1) ═ data 1 × (1+1+1+1) × (1+1-1-1) + data 2: (1-1+1-1) ((1 +1-1-1) + data 3: (1+1-1-1) ((1 +1-1-1) × (1+ 1-1) + data 2 ═ 1-1 ═ data + 3: (1+1+ 1) ═ 0+4 ═ data 3 ═ 4 ═ data. Due to the orthogonality of the orthogonal codes, ONU1 and ONU2 decode to be equal to 0, and only decode data 3 of ONU 3.

In this application, superimposing electrical signals may include superimposing analog electrical signals and superimposing digital electrical signals. The electro-optical conversion module can convert the superposed optical signals into superposed analog electrical signals. Further, optionally, the OLT may further include an analog-to-digital conversion module, and the analog-to-digital conversion module is configured to receive the superimposed analog electrical signal from the photoelectric conversion module, convert the superimposed analog electrical signal into a superimposed digital electrical signal, and transmit the superimposed digital electrical signal to the decoding module. Further, optionally, in order to improve the efficiency of the OLT in recovering the data of the ONUs, the OLT may further include an injection light source. The analog-to-digital conversion module and the injection light source are described in detail, respectively, as follows.

Fifth, analog-to-digital conversion module

If the photoelectric conversion module is of the first structure, the analog-to-digital conversion module is used for receiving the superposed analog electrical signal from the coherent receiver, converting the superposed analog electrical signal into a superposed digital electrical signal and transmitting the superposed digital electrical signal to the decoding module.

And if the photoelectric conversion module is of the second structure, the analog-to-digital conversion module is used for receiving the superposed analog voltage signal from the TIA, converting the superposed analog voltage signal into a superposed digital voltage signal and transmitting the superposed digital voltage signal to the decoding module.

In a possible implementation manner, the analog-to-digital conversion module may be an ADC, and the ADC may be configured to convert an input analog electrical signal into a digital electrical signal and output the digital electrical signal, where the output digital electrical signal is used for the data processing module to process the digital signal. In this way, the ADC in the prior art can be directly multiplexed without the burst ADC, thereby contributing to a reduction in the cost of the integrated OLT.

Further, optionally, the OLT may further include a data processing module, which may be used for recovery of a clock signal, and the like.

Sixthly, injecting light source

In one possible implementation, the injection light source may be a DFB laser, or a multi-wavelength light source lamp.

Two possible ways of emitting the injection light by the injection light source are exemplarily shown below, based on the wavelength of the injection light emitted by the injection light source.

Mode 1, the injection light source emits injection light of a single wavelength.

In one possible implementation, the OLT may further include an injection light source operable to emit a first injection light to each of the M ONUs, respectively. The first injected light may also be referred to as a first seed light. The ONU may generate a first optical carrier having the same wavelength as the first injected light after receiving the first injected light, which may specifically refer to the description of fig. 5a, and details are not repeated here.

Mode 2, the injection light source emits injection light of a plurality of wavelengths.

In a possible implementation, the OLT further includes an injection light source, and the injection light source is configured to respectively emit N second injection lights to each of the M ONUs, where N is an integer greater than 1. After receiving the N second injected lights, the ONU may select one second injected light from the N second injected lights, and generate a second optical carrier having the same wavelength as the selected second injected light, which may specifically refer to the description in fig. 5b, and details are not repeated here.

It should be noted that, if the photoelectric conversion module is the coherent receiver in fig. 7a, the injection light source may also be an intrinsic light source of the coherent receiver. It should be understood that the intrinsic light source of the coherent receiver may also be a separate light source.

In a possible implementation manner, a Medium Access Control (MAC) module may be further included in the OLT, and the MAC module may configure the first configuration information or the second configuration information.

Based on the foregoing, the present application provides an optical communication system. Fig. 8 schematically illustrates an architecture diagram of an optical communication system provided in the present application. The optical communication system may include an OLT, M ONUs, and an ODN, where M is 3 in the example of fig. 8, that is, includes ONU1, ONU2, and ONU3, and the OLT may communicate with ONU1, ONU2, and ONU3 through the ODN, respectively. The ONU can comprise an electro-optical conversion module and an encoding module; the OLT may include a photoelectric conversion module and a decoding module. Further, optionally, the OLT may further comprise an analog-to-digital conversion module, a data processing module, and an injection light source. For the description of the introduction of each module, reference may be made to the above-mentioned related contents, and the description thereof is not repeated here.

Further, optionally, the ODN may include a trunk fiber, an optical splitter, and M branch fibers, where the M branch fibers correspond to the M ONUs one to one, the optical splitter may be connected to each ONU of the M ONUs through a corresponding branch fiber, the OLT is connected to the optical splitter through the trunk fiber, and M is an integer greater than 1. Each ONU in the M ONUs is used for sending a corresponding optical signal to the optical splitter through a corresponding branch optical fiber; the optical splitter is configured to combine the M received optical signals, that is, to converge the optical signals from each of the branch optical fibers to obtain superimposed optical signals, and to send the superimposed optical signals to the OLT through the trunk optical fiber. With reference to fig. 8, ONU1 transmits optical signal 1 to the optical splitter via the corresponding branch optical fiber, ONU2 transmits optical signal 2 to the optical splitter via the corresponding branch optical fiber, and ONU3 transmits optical signal 3 to the optical splitter via the corresponding branch optical fiber. The optical splitter is configured to converge the optical signal 1, the optical signal 2, and the optical signal 3 to obtain a superimposed optical signal, that is, input three optical signals, output one superimposed optical signal, and send the superimposed optical signal to the OLT through the trunk optical fiber. It should be understood that the optical splitter is a passive device, and can simply superpose power on multiple input optical signals.

For the downlink direction, after passing through the optical splitter, one path of optical signal sent by the OLT is divided into M paths of optical signals, which are respectively sent to M ONUs, and each ONU selectively receives downlink data with the same number as the self-set number and discards other data. For example, an injection light source of the OLT emits an optical signal including one path of first injection light, and after passing through an optical splitter, the optical signal is divided into M paths of first injection light, which are respectively sent to M ONUs. With reference to fig. 5a, an injection light source of the OLT emits an optical signal including a first injection light, the optical signal is split into three first injection lights by an optical splitter, and the three first injection lights are respectively sent to the ONU1, the ONU2, and the ONU3 by corresponding branch optical fibers. For another example, an injection light source of the OLT emits one path of optical signals including N second injection lights, and the optical signals are split into M paths of optical signals by an optical splitter, where each path of optical signals includes N second injection lights and is sent to M ONUs respectively. With reference to fig. 5b, the injection light source of the OLT emits an optical signal including three second injection lights in one path, the optical signal is split into three paths by the optical splitter, each path includes three second injection lights, and each path of optical signal is transmitted to the ONU1, the ONU2, and the ONU3 through the corresponding branch optical fiber.

For the uplink direction, the optical splitter may converge the M optical signals from the M ONUs into one superimposed optical signal, and transmit the superimposed optical signal to the OLT through the trunk fiber.

In the optical communication system, the number of wavelengths of the first injection light or the number of wavelengths of the second injection light emitted by the OLT is greater than or equal to the number of ONUs.

The optical communication system in the present application may be a PON system. The PON system may be a gigabit-capable PON (GPON) system, an ethernet passive optical network (ethernet PON, EPON) system, a decagigabit ethernet passive optical network (10Gb/s ethernet passive optical network, 10G-EPON) system, a time and wavelength division multiplexing passive optical network (time and wavelength division multiplexing passive optical network, TWDM-PON), a decagigabit-capable passive optical network (10gigabit-capable passive optical network, XG-PON) system, or a decagigabit-capable symmetric passive optical network (10-gigabit-capable passive optical network, XGs-PON) system, or the like. The new technology of future evolution will improve the speed of PON to 25Gbps, 50Gbps or even 100Gbps, so the application can also apply the PON system with higher transmission speed.

In a possible implementation manner, 64 to 128 ONUs can be included in the PON system. Illustratively, if the PON system includes 64 ONUs, where 32 ONUs need to transmit data, and 32 ONUs do not need to transmit data, based on the above scheme, it may be ensured that the data delay of the 32 ONUs that need to transmit data is as small as possible.

Based on the above, two specific implementations of the optical communication system are given below with reference to specific hardware structures. In order to further understand the architecture of the optical communication system and the implementation process of data transmission.

Fig. 9a is a schematic diagram of an architecture of a PON system according to the present application. The PON system may include ONU1, ONU2, ONU3, OLT, and ODN. The ONU comprises an FDMA encoder or a CDMA encoder and a DFB; the OLT comprises an APD, a TIA, an ADC, a data processing module, an FDMA decoder or a CDMA decoder and an injection light source; the ODN includes trunk fibers, branch fibers, and an optical splitter. It should be understood that if the ONU comprises an FDMA encoder, the OLT comprises an FDMA decoder; if the ONU comprises a CDMA encoder, the OLT comprises a CDMA decoder. The respective structures can be referred to the description of the related contents, and the description is not repeated here.

Fig. 9b is a schematic structural diagram of another PON system provided in the present application. The PON system may include ONU1, ONU2, ONU3, OLT, and ODN. The ONU comprises an FDMA encoder or a CDMA encoder and a DFB; the OLT comprises a coherent receiver, an ADC, a data processing module, an FDMA decoder or a CDMA decoder and an injection light source; the ODN includes trunk fibers, branch fibers, and an optical splitter. It should be understood that if the ONU comprises an FDMA encoder, the OLT comprises an FDMA decoder; if the ONU comprises a CDMA encoder, the OLT comprises a CDMA decoder. The difference from fig. 9a is that the photoelectric conversion module in the PON system is a coherent receiver.

Based on the PON system shown in fig. 9a or 9b, after the data to be sent by the ONU is encoded, the TDMA burst mode of the uplink signal of the PON system in the prior art can be converted into a continuous mode in which all ONUs send data, and the problems faced by the burst mode of the PON system in the prior art, such as high difficulty in burst TIA technology, immature burst ADC industrial chain, and the like, can be solved.

Based on the above and the same concept, the present application also provides a data transmission method. Referring to fig. 10, the method can be applied to the system shown in fig. 1, fig. 8, fig. 9a or fig. 9 b. The data transmission method may include the following steps.

Step 1001, the ONU performs orthogonality encoding on data to be transmitted to obtain an electrical signal.

The following exemplarily shows two implementations of orthogonal coding of data to be transmitted by ONUs.

The step 1001 may be executed by an encoding module in the ONU, and a possible implementation manner may refer to the introduction of the encoding module, which is not described herein repeatedly.

In step 1002, the ONU converts the electrical signal into an optical signal and transmits the optical signal to the ODN.

Illustratively, the optical communication system includes M ONUs, and in a possible implementation, each ONU of the M ONUs may receive a first injection light transmitted from the OLT, generate a first optical carrier according to the first injection light, and modulate an electrical signal onto the first optical carrier to obtain an optical signal, where a wavelength of the first optical carrier is equal to a wavelength of the first injection light. In another possible implementation manner, each ONU of the M ONUs may respectively receive N second injected lights from the OLT, select one second injected light from the N second injected lights, generate a second optical carrier according to the selected second injected light, modulate an electrical signal onto the second optical carrier, and obtain an optical signal, where a wavelength of the second optical carrier is the same as a wavelength of the selected second injected light, and N is an integer greater than 1.

This step 1002 can be executed by the above-mentioned electrical-to-optical conversion module, and possible implementation manners can be referred to the description of the above-mentioned electrical-to-optical conversion module, and will not be described repeatedly herein.

In step 1003, the ODN superimposes M optical signals from the M ONUs to obtain a superimposed optical signal, and sends the superimposed optical signal to the OLT. Accordingly, the OLT receives the superimposed optical signal through the ODN.

This step 1003 is an optional step. Possible implementations of ODNs are described above and will not be repeated here.

In step 1004, the OLT converts the received superimposed optical signal into a superimposed electrical signal.

Here, the superimposed electrical signals include M electrical signals orthogonal to each other, the M electrical signals correspond to the M optical signals one to one, the M ONUs correspond to the M optical signals one to one, and M is an integer greater than 1.

In a possible implementation manner, the method may further include receiving the intrinsic light, performing a mixing process on the intrinsic light and the superimposed optical signal to obtain a mixed signal, and converting the mixed signal into a superimposed electrical signal.

The step 1004 may be executed by the photoelectric conversion module, and reference may be made to the description of the photoelectric conversion module in possible implementation manners, which is not repeated herein.

In step 1005, the OLT may decode according to the superimposed electrical signal to obtain data sent by each ONU of the M ONUs.

The following exemplarily shows two implementations of decoding.

Step 1005 may be performed by the decoding module, and possible implementation manners may refer to the description of the decoding module, which is not repeated herein.

In one possible implementation, the superimposed electrical signals include superimposed analog electrical signals and superimposed digital electrical signals; the superimposed electrical signal received by the OLT is a superimposed analog electrical signal. Further, the superimposed analog electrical signal may be converted to a superimposed digital electrical signal.

As can be seen from steps 1001 to 1005, the ONUs perform orthogonality encoding on data to be transmitted to obtain electrical signals, and because the electrical signals obtained by different ONUs are orthogonal to each other, the electrical signals obtained by different ONUs are different from each other and orthogonal to each other. If a plurality of ONUs need to send data, the electrical signals of the ONUs do not interfere with each other, and the ONUs can simultaneously transmit optical signals to the OLT, that is, the data of the ONUs can overlap in time. In this way, data of multiple ONUs can simultaneously reach the OLT, which helps to reduce the delay of data sent by the ONUs. It is equivalent to that each ONU establishes a logical point-to-point link with the OLT (i.e. the ONU and the OLT are point-to-point independent transmission channels), and different links do not interfere with each other.

In the embodiments of the present application, unless otherwise specified or conflicting with respect to logic, the terms and/or descriptions in different embodiments have consistency and may be mutually cited, and technical features in different embodiments may be combined to form a new embodiment according to their inherent logic relationship.

In the present application, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone, wherein A and B can be singular or plural. In the description of the text of this application, the character "/" generally indicates that the former and latter associated objects are in an "or" relationship. In the formula of the present application, the character "/" indicates that the preceding and following related objects are in a relationship of "division".

It is to be understood that the various numerical designations referred to in this application are merely for ease of description and are not intended to limit the scope of the embodiments of the present application. The sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of the processes should be determined by their functions and inherent logic. The terms "first," "second," and the like, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. Furthermore, the terms "comprises" and "comprising," as well as any variations thereof, are intended to cover a non-exclusive inclusion, such as a list of steps or elements. A method, system, article, or apparatus is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, system, article, or apparatus.

Although the present application has been described in conjunction with specific features and embodiments thereof, it will be evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the application. Accordingly, the specification and figures are merely illustrative of the concepts defined by the appended claims and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of the application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to encompass such modifications and variations.

Claims

1. An optical network unit ONU is characterized by comprising an encoding module and an electro-optical conversion module;

the encoding module is used for performing orthogonality encoding on data to be transmitted to obtain an electric signal and transmitting the electric signal to the electro-optical conversion module;

the electro-optical conversion module is configured to convert the received electrical signal into an optical signal, and send the optical signal to an optical line terminal OLT through an optical distribution network ODN.

2. The ONU of claim 1, wherein the encoding module is a frequency division multiplexing access, FDMA, encoder;

the encoding module is specifically configured to:

determining a frequency band corresponding to the ONU;

and multiplying the data and the corresponding frequency band to obtain the electric signal.

3. The ONU of claim 1 or 2, wherein the encoding module is further configured to:

receiving first configuration information from the OLT, wherein the first configuration information comprises a frequency band corresponding to the ONU.

4. The ONU of claim 1, wherein the encoding module is a code division multiple access CDMA encoder;

the encoding module is specifically configured to:

determining a code word corresponding to the ONU;

and multiplying the data and the corresponding code word to obtain the electric signal.

5. The ONU of claim 1 or 4, wherein the encoding module is further configured to:

and receiving second configuration information from the OLT, wherein the second configuration information comprises a code word corresponding to the ONU.

6. The ONU according to any of claims 1 to 5, wherein the electrical-to-optical conversion module is specifically configured to:

receiving first injection light emitted by an injection light source from the OLT;

generating a first optical carrier according to the first injected light, wherein the wavelength of the first optical carrier is equal to that of the first injected light;

and modulating the electric signal to the first optical carrier to obtain the optical signal.

7. The ONU according to any of claims 1 to 5, wherein the electrical-to-optical conversion module is specifically configured to:

receiving N second injection lights emitted by an injection light source from the OLT, wherein N is an integer greater than 1;

generating a second optical carrier according to the N second injected lights, wherein the wavelength of the second optical carrier is the same as the wavelength of one of the N second injected lights;

and modulating the electric signal to the second optical carrier to obtain the optical signal.

8. An optical line terminal OLT is characterized by comprising a photoelectric conversion module and a decoding module;

the optical-electrical conversion module is configured to receive an optical add-on signal through an optical distribution network ODN, convert the optical add-on signal into an electrical add-on signal, and transmit the electrical add-on signal to the decoding module, where the optical add-on signal is obtained by adding M optical signals from M optical network units ONU, the electrical add-on signal includes M electrical signals orthogonal to each other, the M electrical signals correspond to the M optical signals one to one, the M ONU corresponds to the M optical signals one to one, and M is an integer greater than 1;

and the decoding module is used for decoding according to the superposed electric signals to obtain data sent by each ONU in the M ONUs.

9. The OLT of claim 8, wherein the decoding module is a Frequency Division Multiplexing Access (FDMA) decoder comprising K filters, wherein K is a positive integer, and wherein the frequency bands allowed to pass through each of the K filters is different;

each filter in the K filters is configured to allow an electrical signal in a corresponding frequency band in the superimposed electrical signal to pass through, one ONU corresponds to one frequency band, and the frequency bands corresponding to any two ONUs do not overlap with each other.

10. The OLT of claim 8, wherein the decoding module is a Code Division Multiple Access (CDMA) decoder;

the CDMA decoder is used for performing multiply-accumulate operation on the code word corresponding to each ONU in the M ONUs and the superposed electric signal to obtain data sent by each ONU in the M ONUs, wherein one ONU corresponds to one code word, and any two code words are orthogonal to each other.

11. The OLT of any of claims 8-10, wherein the OLT further comprises an injection light source;

the injection light source is used for respectively emitting first injection light to each ONU in the M ONUs;

the first injected light is used for the ONU to generate a first optical carrier, the first optical carrier is used for carrying an electrical signal of the ONU, and a wavelength of the first optical carrier is the same as a wavelength of the first injected light.

12. The OLT of any of claims 8-10, wherein the OLT further comprises an injection light source;

the injection light source is configured to emit N second injection lights to each of the M ONUs, respectively;

the N second injection lights are used for the ONU to generate a second optical carrier, the second optical carrier is used for carrying an electrical signal of the ONU, wavelengths of the N second injection lights are different, the wavelength of the second optical carrier is the same as the wavelength of one of the N second injection lights, and N is an integer greater than 1.

13. The OLT of any of claims 8 to 12, wherein the optical-to-electrical conversion module is a coherent receiver comprising an intrinsic light source, an optical mixer, and a balanced detector;

the intrinsic light source is used for emitting intrinsic light to the optical mixer;

the optical mixer is used for carrying out frequency mixing processing on the received intrinsic light and the superimposed optical signal to obtain a frequency mixing signal and transmitting the frequency mixing signal to the balance detector;

and the balance detector is used for converting the mixing signal into a superimposed electric signal and transmitting the superimposed electric signal to the decoding module.

14. The OLT of any of claims 8 to 12, wherein the photoelectric conversion module comprises an Avalanche Photodiode (APD) and a transimpedance amplifier (TIA);

the APD is used for receiving the superposed optical signal, converting the superposed optical signal into a superposed current signal and transmitting the superposed current signal to the TIA;

and the TIA is used for converting the received superposed current signal into a superposed voltage signal.

15. The OLT of any of claims 8-14, wherein the superimposed electrical signals comprise superimposed analog electrical signals and superimposed digital electrical signals; the OLT also comprises an analog-to-digital conversion module;

the analog-to-digital conversion module is used for receiving the superposed analog electrical signal from the photoelectric conversion module, converting the superposed analog electrical signal into a superposed digital electrical signal and transmitting the superposed digital electrical signal to the decoding module.

16. An optical communication system comprising M optical network units ONU according to any of claims 1 to 7, an optical line terminal OLT according to any of claims 8 to 15, and an optical distribution network ODN;

wherein the OLT communicates with each of the M ONUs through the ODN.

17. The optical communication system of claim 16, wherein the ODN comprises a trunk fiber, an optical splitter and M branch fibers, the M branch fibers correspond to the M ONUs one-to-one, the optical splitter is connected to each of the M ONUs through a corresponding branch fiber, the OLT and the optical splitter are connected through the trunk fiber, and M is an integer greater than 1;

each of the M ONUs is configured to transmit an optical signal to the optical splitter through the corresponding branch optical fiber;

the optical splitter is configured to combine the M received optical signals to obtain the superimposed optical signal, and send the superimposed optical signal to the OLT through the trunk optical fiber.

18. A data transmission method is applied to an Optical Network Unit (ONU), and comprises the following steps:

carrying out orthogonality coding on data to be transmitted to obtain an electric signal;

and converting the electric signal into an optical signal, and sending the optical signal to an optical line terminal OLT through an optical distribution network ODN.

19. The method of claim 18, wherein said orthogonalizing the data to be transmitted to obtain an electrical signal comprises:

determining a frequency band corresponding to the ONU;

20. The method of claim 18 or 19, wherein the method further comprises:

21. The method of claim 18, wherein said orthogonalizing the data to be transmitted to obtain an electrical signal comprises:

determining a code word corresponding to the ONU;

22. The method of claim 18 or 21, wherein the method further comprises:

23. The method of any of claims 18 to 22, wherein said converting the electrical signal to an optical signal comprises:

receiving a first injected light emitted from the OLT;

24. The method of any of claims 18 to 22, wherein said converting the electrical signal to an optical signal comprises:

receiving N second injected lights emitted from the OLT, wherein N is an integer greater than 1;

25. A data transmission method is applied to an Optical Line Terminal (OLT), and comprises the following steps:

receiving the superimposed optical signal by an Optical Distribution Network (ODN);

converting the superimposed optical signals into superimposed electrical signals, wherein the superimposed optical signals are obtained by superimposing M optical signals from M Optical Network Units (ONU), the superimposed electrical signals comprise M mutually orthogonal electrical signals, the M electrical signals correspond to the M optical signals one by one, the M ONU corresponds to the M optical signals one by one, and M is an integer greater than 1;

and decoding according to the superposed electric signals to obtain data sent by each ONU in the M ONUs.

26. The method of claim 25, wherein said decoding from the superimposed electrical signal to obtain the data sent by each of the M ONUs comprises:

and respectively allowing the electric signals of the corresponding frequency bands in the superposed electric signals to pass through to obtain the data sent by each ONU in the M ONUs, wherein one ONU corresponds to one frequency band, and the frequency bands corresponding to any two ONUs are not overlapped with each other.

27. The method of claim 25, wherein said decoding from the superimposed electrical signal comprises:

and performing multiply-accumulate operation on the code word corresponding to each ONU in the M ONUs and the superposed electric signal to obtain data sent by each ONU, wherein one ONU corresponds to one code word, and any two code words are orthogonal to each other.

28. The method of any one of claims 25 to 27, further comprising:

transmitting a first injection light to each of the M ONUs, respectively;

29. The method of any one of claims 25 to 27, further comprising:

transmitting N second injection lights to each ONU in the M ONUs respectively;

30. The method of any one of claims 25 to 29, wherein said converting the superimposed optical signal into a superimposed electrical signal comprises:

receiving the intrinsic light;

mixing the intrinsic light and the superposed light signal to obtain a mixed signal;

the mixed signal is converted into a superimposed electrical signal.

31. The method of any one of claims 25 to 29, wherein said converting the superimposed optical signal into a superimposed electrical signal comprises:

converting the superimposed optical signal into a superimposed current signal;

and converting the superposed current signal into a superposed voltage signal.

32. The method of any one of claims 25 to 31, wherein the superimposed electrical signals comprise superimposed analog electrical signals and superimposed digital electrical signals;

the method further comprises the following steps:

and receiving the superposed analog electrical signal from the photoelectric conversion module, and converting the superposed analog electrical signal into a superposed digital electrical signal.