WO2014040272A1

WO2014040272A1 - Method, device and system for coherent receiving signal

Info

Publication number: WO2014040272A1
Application number: PCT/CN2012/081407
Authority: WO
Inventors: 周雷; 彭桂开
Original assignee: 华为技术有限公司
Priority date: 2012-09-14
Filing date: 2012-09-14
Publication date: 2014-03-20
Also published as: CN103004111B; CN103004111A

Abstract

A method for coherent receiving signal is disclosed in the embodiment of the present invention. In the method, a direct-current non-modulation downlink optical signal is extracted by an optical filter, and then is used for coherent receiving the downlink optical signal as its polarized light. Modulation and amplification of uplink optical signal is completed by a reflective type photoelectric device. By this way, under the condition of no polarized laser with polarization diversity configuration and coherent reception, the terminal will implement coherent reception with low cost.

Description

Coherent receiving signal method, device and system

Technical field

The invention belongs to the field of communications, and in particular relates to a coherent receiving signal method, device and system. Background technique

Passive Optical Network (POS) has gradually become the mainstream technology in the field of broadband access. A typical P0S system is connected to a beam splitter (Splitter) through a fiber optic cable (Multiple Optical Network Unit, ONU). After convergence, it is connected to the Optical Line Terminate (OLT) through the backbone fiber. During the network upgrade process, the Optical Distribution Network (ODN) needs to remain unchanged, that is, the Splitter-based ODN structure is unchanged.

In Subcarrier Muplexplexing (SCM)/Orthogonal Frequency Division Multiplexing (OFDM), each ONU corresponds to one channel, and each channel corresponds to one subcarrier frequency SCI, SC2, SC3, . ..SCN, the data of each ONU is modulated onto the corresponding subcarriers respectively, and the modulation format can achieve the purpose of compressing the signal bandwidth by using flexible high-order modulation 16/64/128 Quadrature Amplitude Modulation (QAM). All the channels are combined in the electrical domain, modulated into optical signals, transmitted through the optical fiber, and photoelectrically converted at the receiving end, and each terminal uses an electrical filter to select its own subcarrier. Another advantage of SCM is that bandwidth can be scheduled from the subcarrier level between ONUs, and this architecture can be based on Splitter and is compatible with existing ODN networks.

In the prior art, a hybrid PON system of Ultra Dense Wavelength Division Multiplexing Orthogonal Frequency Division Multiplexing (UDWDM-OFDM) can guarantee UDWDM.

The bandwidth of the PON optoelectronic device is unchanged. The spectrum compression feature of OFDM is used to transmit more data, improve the bandwidth of the end user, and utilize the characteristics of flexible scheduling of OFDM bandwidth to dynamically allocate and adjust the bandwidth of the end user. At the same time, the coherent reception technology can greatly improve the receiver sensitivity, and the customer service OFDM reception is less sensitive, which satisfies the system with sufficient power budget. However, the disadvantage is that the ONU requires a polarization diversity structure, and the complexity of the device is increased by 2 times. At the same time, the ONU requires a high-precision adjustable laser with high cost. As a local oscillator laser for coherent reception, the above two conditions lead to excessive terminal cost and cannot be applied in engineering.

Therefore, how to enable the terminal to achieve low-cost coherent reception under the condition of no polarization diversity structure and coherently received local oscillator laser is an urgent problem to be solved. Summary of the invention

In view of this, embodiments of the present invention provide a method, device, and system for coherent reception of signals, so that the terminal can achieve low-cost coherent reception under the conditions of a non-polarization diversity structure and a coherently received local oscillator laser.

In a first aspect, a method for coherent reception of signals includes:

Receiving, by the central end device, the first downlink optical signal sent by the central device to the terminal device, dividing the first downlink optical signal into two paths, where one path is used as signal light, and the other path is used to generate the signal light. Vibrating, coherently receiving the signal light and the local oscillator light.

In a first possible implementation manner of the first aspect, the method further includes: combining the first aspect or the first possible implementation manner of the first aspect, where The first downlink optical signal is divided into two paths, wherein one path is used as the signal light, and the other path is used to generate the local oscillator light of the signal light, including:

The first downlink optical signal is divided into two paths, wherein one channel is used as the second downlink optical signal input coupler; the other circuit is filtered to obtain a third downlink optical signal with no DC signal modulation;

The first upstream optical signal is directly loaded onto the DC non-signal modulated third downlink optical signal, and the modulated third downlink optical signal is used as the second upstream optical signal;

And dividing the second uplink optical signal into two paths, where one channel is output to the central office device, and the other circuit is filtered to obtain a third uplink optical signal with no DC signal modulation, and the DC signalless modulation is performed. The third upstream optical signal is input to the coupler as the local oscillator light of the second downstream optical signal.

With reference to the first aspect, the first possible implementation manner of the first aspect, or the second possible implementation manner of the first aspect, in a third possible implementation manner, after the second uplink optical signal is deflected And inputting the central office device, so that a deflection state of the deflected second upstream optical signal is perpendicular to a deflection state of the first downstream optical signal.

Combining the first aspect, the first possible implementation manner of the first aspect, the second The implementation of the energy or the third possible implementation manner of the first aspect, in the fourth possible implementation manner, the first downlink optical signal is divided into two paths, wherein one channel is used as the signal light, The local oscillator that uses another path for generating the signal light specifically includes:

The first downlink optical signal is divided into two paths, wherein one channel is used as the second downlink optical signal input coupler; the other circuit is filtered to obtain the third downlink optical signal with no DC signal modulation, and the amplified DC is obtained. a third downstream optical signal modulated by the signal;

And dividing the amplified DC signal-free third downlink optical signal into two paths according to a certain ratio, wherein one path is used as a local oscillator optical input coupler of the second downlink optical signal; and the second uplink optical signal is obtained through another path. ;

The first upstream optical signal is directly loaded to another path of the amplified DC signal-free modulated third downlink signal, and the second uplink optical signal is obtained and output to the central office equipment.

Combining the first aspect, the first possible implementation of the first aspect, the second possible implementation of the first aspect, the third possible implementation of the first aspect, or the fourth possible aspect of the first aspect In an implementation manner, the method further includes:

The second upstream optical signal is subjected to a deflection process and then input to the central office device such that a deflection state of the deflected second upstream optical signal is perpendicular to a deflection state of the first downstream optical signal.

In a second aspect, a coherent receiving signal device includes:

a receiving unit, configured to receive a downlink optical signal input by the central office;

a first processing unit, configured to divide the first downlink optical signal into two paths, where one path is used as signal light, and the other path is used to generate local light of the signal light;

a coupler for coherently receiving the signal light and the local oscillator light.

With reference to the second aspect, in a first possible implementation manner of the second aspect, the device further includes: combining the second aspect or the first possible implementation manner of the second aspect, the second possible aspect in the second aspect The first processing unit specifically includes:

a first circulator, configured to output a first downlink optical signal to the first optical splitter;

The first optical splitter is configured to divide the first downlink optical signal into two paths, wherein one channel is used as a second downlink optical signal input coupler; the other channel is input to the second circulator;

The second circulator is configured to transmit another path divided by the first downlink optical signal to the optical filter The optical filter is configured to process another path divided by the first downlink optical signal to obtain a third downlink optical signal that is DC-free modulated;

a reflective semiconductor optical amplifier, configured to directly load the first upstream optical signal onto the third downlink optical signal that is not modulated by the DC signal, and use the modulated DC non-signal third downlink optical signal as the second upstream optical Signal

a second optical splitter, configured to divide the second upstream optical signal into two paths, where one input is input to the first circulator and the other input to the optical filter;

The first circulator is further configured to output the path of dividing the second upstream optical signal to the central office device;

The optical filter is further configured to process another path into which the second upstream optical signal is divided to obtain a third upstream optical signal that is DC-free modulated;

The second circulator is further configured to input the DC signal-free third uplink optical signal as the local oscillator light of the second downlink optical signal into the coupler.

With reference to the second aspect, the first possible implementation manner of the second aspect, or the second possible implementation manner of the second aspect, in a third possible implementation manner of the second aspect, Includes:

The second circulator is configured to transmit another path that divides the first downlink optical signal to an optical filter;

The optical filter is configured to process another path divided by the first downlink optical signal to obtain a third downlink optical signal that is DC-free modulated;

The first circulator is further configured to output the second uplink optical signal into one end to the central office device; The optical filter is further configured to process another path into which the second upstream optical signal is divided to obtain a third uplink optical signal that is DC-free modulated;

With reference to the second aspect, the first possible implementation of the second aspect, the second possible implementation of the second aspect, or the third possible implementation of the second aspect, the fourth aspect of the second aspect In a possible implementation, the device further includes a polarization rotator, and the polarization rotator is configured to perform the deflection processing on the second upstream optical signal, and then input the central end device, so that the deflected second upstream optical signal The deflection state is perpendicular to the deflection state of the first downstream optical signal.

Combining the second aspect, the first possible implementation of the second aspect, the second possible implementation of the second aspect, the third possible implementation of the second aspect, or the fourth possibility of the second aspect In a fifth possible implementation manner of the second aspect, the first processing unit specifically includes:

a circulator: for outputting a first downstream optical signal to the first optical splitter;

The first optical splitter is configured to divide the first downlink optical signal into two paths, wherein one path is used as a second downlink optical signal input coupler; and the other input optical filter is used;

The optical filter is configured to process another path that is divided by the first downlink optical signal to obtain a third downlink optical signal that is DC-free modulated;

a semiconductor optical amplifier, configured to amplify the third downlink optical signal modulated by the DC signal to obtain an amplified DC signal-free third downlink optical signal;

a second beam splitter, configured to divide the amplified DC signal-free third downlink optical signal into two paths, wherein one path of the local oscillator as the second downlink optical signal is input to the coupler, and the other path Input modulator

The modulator is configured to directly load the first upstream optical signal to another path of the amplified DC signal-free modulated third downlink optical signal to obtain a second uplink optical signal;

The circulator is further configured to output the second uplink optical signal to the central office device.

Combining the second aspect, the first possible implementation of the second aspect, the second possible implementation of the second aspect, the third possible implementation in the second aspect, and the fourth possible aspect of the second aspect In a sixth possible implementation manner of the second aspect, the device further includes a yaw rotator, wherein the polarization rotator is configured to Two The uplink optical signal is subjected to a deflection process and then input to the central office device, so that the deflection state of the deflected second upstream optical signal is perpendicular to the deflection state of the first downstream optical signal.

In a third aspect, a central office apparatus includes the various features of a coherent received signal device and combinations of various features described in the second aspect above.

In a fourth aspect, a terminal device comprising the various features of a coherent received signal device and combinations of various features described in the second aspect above.

A fifth aspect, a passive optical network system, comprising the central office device according to the third aspect and/or the terminal device according to the fourth aspect.

In the embodiment of the present invention, the local oscillator light that is coherently received with the downlink optical signal is generated by the terminal from the downlink optical signal, and the laser with high cost and precise wavelength is not required as the local oscillator laser; the wavelength of the local oscillator optical signal is the downward light. The signal wavelength is obtained by injecting the center wavelength of the downstream optical signal into the reflective photoelectric device. After coherent with the second downstream optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the bandwidth required by the subsequent electrical device, without any need. The wavelength control mechanism; the polarization state of the downstream optical signal is transmitted through the ODN, and the polarization state is random after reaching the terminal. The usual coherent receiving structure is a polarization diversity mode, and two sets of the same structure are used to respectively receive the two polarizations of the optical signal. In the present invention, the local oscillator signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the correct coherent reception can be completed without the polarization diversity structure, and the device complexity is doubled; Optoelectronic devices are typically operated in a saturated state, and the reflective optoelectronic device erases the downward light. After the number, the uplink data is modulated onto the reflective optoelectronic device. Since the optical signal injected into the reflective optoelectronic device is already unmodulated DC light, there is no need to require the reflective optoelectronic device to be saturated (saturation requires higher injected optical power) ), directly modulating the uplink data onto the light, reducing the requirement of the optical signal power injected into the reflective optoelectronic device, and significantly improving the downlink optical power budget; a reflective optoelectronic device + optical filter structure, and completing the downlink The generation and amplification of the oscillating direct current and the modulation transmission function of the upstream signal. There is no need for an additional laser as the upstream source, which minimizes the required optical components on the terminal side and is extremely cost effective.

In the embodiment of the present invention, the local oscillator light that is coherently received with the downlink optical signal is generated by the terminal from the downlink optical signal, and the laser with high cost and precise wavelength is not required as the local oscillator laser; the wavelength of the local oscillator optical signal is the downward light. The signal wavelength is obtained by injecting the center wavelength of the downstream optical signal into the semiconductor optical amplifier. After coherent with the second downstream optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the bandwidth required by the subsequent electrical device, without any wavelength. Control mechanism; the polarization state of the downstream optical signal is transmitted through the ODN, and after reaching the terminal, its polarization state is random, and the usual coherent receiving structure is polarization diversity. In the present invention, two sets of the same structure are used to respectively receive two polarization states of the optical signal. In the present invention, the local oscillator optical signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the polarization diversity structure is not required. The correct coherent reception can be completed, and the complexity of the device is doubled. A semiconductor optical amplifier + optical filter + modulator structure completes the generation of the local oscillator DC light, the amplification and the modulation transmission function of the uplink signal, without additional As an upstream light source, the laser reduces the required optical components on the terminal side to a minimum, which is extremely cost-effective. After the optical filter on the ONU side, the semiconductor optical amplifier only amplifies the direct current light and divides it into two paths, one of which enters The 2x2 coupler acts as the local oscillator of the downstream optical signal, and the other passes through a modulator, and the upstream signal is modulated onto the optical through the modulator. This prevents the upstream optical signal from being filtered by the optical filter, and the spectrum utilization rate is higher. . DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the present invention. It will be apparent to those skilled in the art that other drawings may be obtained from these drawings without the inventive labor.

1 is a flowchart of a method for coherently receiving signals according to an embodiment of the present invention;

2 is a structural diagram of a coherent receiving signal device according to an embodiment of the present invention;

3 is a structural diagram of an OFDM passive optical network system according to an embodiment of the present invention; FIG. 4 is a structural diagram of another OFDM passive optical network system according to an embodiment of the present invention; FIG. 6 is a flowchart of a method for coherently receiving signals according to an embodiment of the present invention; FIG.

7 is a structural diagram of a coherent receiving signal device according to an embodiment of the present invention;

FIG. 8 is a structural diagram of an OFDM passive optical network system according to an embodiment of the present invention; FIG. 9 is a structural diagram of another OFDM passive optical network system according to an embodiment of the present invention; Another structural diagram of an OFDM passive optical network system is provided. detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to be limiting. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

A coherent received signal method and system, and a coherent device provided by the embodiments of the present invention enable low-cost coherent reception under the conditions of a non-polarization diversity structure and a coherently received local oscillator laser. The following description will be made by way of specific examples.

Embodiment 1:

Referring to FIG. 1, FIG. 1 is a flowchart of a method for coherently receiving signals according to an embodiment of the present invention. As shown in FIG. 1, the coherent reception signal method may include the following steps:

As a preferred embodiment, the method further includes:

101. Receive a first downlink optical signal sent by the central office device to the terminal device.

102, the first downlink optical signal is divided into two paths, wherein one path is used as the second downlink optical signal input coupler; the other path is filtered to obtain the third downlink optical signal with no DC signal modulation; The first downstream optical signal passing through the first circulator is divided into two paths, wherein one path is input as a second downlink optical signal to the 2x2 coupler; the other path is passed through the second circulator and then input to the optical filter for processing. , obtaining a third downlink optical signal with no signal modulation of DC.

In the embodiment of the present invention, the first downlink optical signal of the central office is an optical signal sent by the central office to the terminal. The central office generates a multi-band OFDM electrical signal, and the downlink data information is modulated in a passband, and a certain frequency interval is set between the baseband (DC) and the baseband (DC). Here, each subband can correspond to one terminal, or multiple terminals can share one subband, and subcarrier scheduling in the subband is used to complete broadband allocation. The OFDM electrical signal modulates the signal on the light through the modulator. The modulated spectrum has a certain frequency interval between the wavelength of the signal light and the center wavelength of the laser, and this frequency interval is the same as the frequency interval between the passband and the baseband of the electrical domain. The modulated optical signal passes through the circulator and is sent to the ODN. After the splitter, it reaches each ONU.

At the ONU, after the first downstream optical signal passes through the first circulator, it is divided into two paths, one of which directly enters the 2x2 coupler, and the other passes through the second circulator and then inputs an optical filter, which is an optical bandpass The filter, the center wavelength is the center wavelength of the downstream laser, and the bandwidth is only allowed to pass through the baseband DC component. Cause A part of the energy of the first downstream optical signal is distributed at the center wavelength of the signal-free modulation (the central unmodulated DC optical carrier is 25 dB from the signal frequency band), and after passing through the optical filter, the spectral components of the signal are filtered out to obtain a direct current ( That is, continuous) optical signals without signal modulation. Such an optical signal conforms to the local oscillator condition as a coherent reception.

103. The first uplink optical signal is directly loaded onto the DC downlink signal that is not modulated by the DC signal, and the modulated third downlink optical signal is used as the second uplink optical signal.

In this step, the first upstream optical signal is directly loaded onto the DC non-signal modulated third downlink optical signal by the reflective optoelectronic device to obtain a second upstream optical signal.

In the embodiment of the present invention, the first downlink optical signal is divided into two paths after passing through the first circulator, wherein one channel is input as a second downlink optical signal to the 2x2 coupler; the other channel is processed through the second circulator and then input to the optical filter. , thereby obtaining a third downlink optical signal that is DC-free signal-modulated. The filtered DC light is injected into the reflective optoelectronic device. The reflective optoelectronic device has two functions: First, after the DC light is injected into the reflective optoelectronic device, the center wavelength of the output of the reflective optoelectronic device is consistent with the center wavelength of the first downstream optical signal; second, the uplink OFDM The data information is modulated onto the light by a reflective optoelectronic device while the reflective optoelectronic device amplifies the upstream signal. Here, the modulation idea of the upstream optical signal is consistent with the downlink optical signal, and the signal is modulated to the passband, and a certain frequency interval is set with the baseband. Similarly, the output of the obtained upstream optical signal modulates the spectrum, and the center wavelength is still DC light without signal modulation, and the power is significantly amplified.

104, dividing the second uplink optical signal into two paths, where one channel is output to the central office device, and the other circuit is filtered to obtain a third uplink optical signal with no DC signal modulation, and the DC current is not Transmitting the third upstream optical signal of the signal as the local oscillator of the second downstream optical signal to the coupler;

In this step, the second uplink optical signal is divided into two paths, wherein one path is output to the OLT through the first circulator, and the other path is passed through the optical filter to obtain a third dc-free signal modulation. Upstream optical signal, and the third uplink optical signal modulated by the DC signal is used as the local oscillator of the second downlink optical signal, and is input to the 2x2 coupler through the second circulator, and is coupled by the 2x2 The device performs coherent reception on the local oscillator lights of the second downlink optical signal and the second downlink optical signal.

In the embodiment of the present invention, the optical signal output from the reflective optoelectronic device is divided into two paths, one of which is input to the first circulator, and is sent as an upstream optical signal to the OLT; the other passes through the optical filter again, and the uplink signal data information is just right. Filtered by the optical filter to obtain an amplified DC optical signal, passing through the second ring The device inputs a 2x2 coupler as a local oscillator of the second downstream optical signal, and performs coherent reception on the second downstream optical signal.

105. Perform coherent reception on the second downlink signal light and the local oscillator light of the second downlink optical signal.

The advantages of the embodiments of the present invention are as follows: First, the terminal side does not need a costly laser with a precisely adjustable wavelength as the local oscillator laser; second, the wavelength of the local oscillator optical signal is the wavelength of the downstream optical signal, because the downlink is The center wavelength of the optical signal is injected into the reflective optoelectronic device. After being coherent with the second downlink optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the required bandwidth of the subsequent electrical device, and does not require any wavelength control mechanism. Third, the polarization state of the downstream optical signal is transmitted through the ODN and reaches the terminal. , its polarization state is random. A typical coherent receiving structure is a polarization diversity mode in which two sets of identical structures are used to receive two polarization states of an optical signal, respectively. In the present invention, the local oscillator signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the correct coherent reception can be completed without the polarization diversity structure. The device complexity is doubled. Fourth, the reflective optoelectronic device is usually operated in a saturated state. After the reflective optoelectronic device erases the downstream optical signal, the upstream data is modulated onto the reflective optoelectronic device. Here, since the optical signal such as to the reflective optoelectronic device is already unmodulated DC light, it is not necessary to require the reflection type photovoltaic device to be saturated (saturation requires a higher injection optical power), and the uplink data can be directly modulated onto the light. The requirement of the optical signal power of the injected reflective optoelectronic device is reduced, and the downlink optical power budget is obviously improved; fifth, a reflective optoelectronic device + optical filter structure, simultaneously completing the generation, amplification and uplink signals of the downlink local oscillator DC light Modulation send function. No additional laser is required as the upstream source. Minimizing the required optical components on the terminal side is extremely cost effective.

Embodiment 2:

Referring to FIG. 2, FIG. 2 is a structural diagram of a coherent receiving signal device according to an embodiment of the present invention. As shown in FIG. 2, the coherent receiving signal device may include the following devices:

The first circulator 201 is configured to output a first downstream optical signal to the first optical splitter 202;

The first optical splitter 202 is configured to split the first downlink optical signal into two paths, where one path is used as the second downlink optical signal input coupler 203; the other input is input to the second circulator 204, where The coupler can be a 2x2 coupler;

The second circulator 204 is configured to transmit the other path of the first downstream optical signal to the optical filter 205;

In the embodiment of the present invention, the first downlink optical signal of the central office is an optical signal sent by the central office to the terminal. Central office A multi-band OFDM electrical signal is generated, and downlink data information is modulated in a pass band, and a certain frequency interval is set between the baseband (DC) and the baseband (DC). Here, each subband can correspond to one terminal, or multiple terminals can share one subband, and subcarrier scheduling in the subband is used to complete broadband allocation. The OFDM electrical signal modulates the signal on the light through the modulator. The modulated spectrum has a certain frequency interval between the wavelength of the signal light and the center wavelength of the laser, and the frequency interval is the same as the frequency interval between the passband and the baseband of the electrical domain. The modulated optical signal passes through the circulator and is sent to the ODN. After the splitter, it reaches each ONU.

At the ONU, after the first downstream optical signal passes through the first circulator 201, it is divided into two paths, one of which directly enters the 2x2 coupler 203, and the other passes through the second circulator 204 and is input to the optical filter 205. 205 is an optical bandpass filter, the center wavelength is the center wavelength of the downstream laser, and the bandwidth is only allowed to pass through the baseband DC component. Because a part of the energy of the first downlink optical signal is distributed at the center wavelength of the signalless modulation (the central unmodulated DC optical carrier is 25 dB larger than the signal frequency band), after passing through the optical filter 205, the signal spectral components are filtered out to obtain a direct current. (ie continuous) optical signals without signal modulation. Such an optical signal conforms to the local oscillator condition as a coherent reception.

The optical filter 205 is configured to process another path divided by the first downlink optical signal to obtain a third downlink optical signal that is DC-free modulated.

The reflective optoelectronic device 207 is configured to directly load the first upstream optical signal onto the DC non-signal modulated third downlink optical signal to obtain the second upstream optical signal.

In the embodiment of the present invention, the first downlink optical signal is divided into two paths after passing through the first circulator 201, wherein one path is input as the second downlink optical signal to the 2x2 coupler 203; the other path is input to the optical filter after passing through the second circulator 204. The processor 205 performs processing to obtain a third downlink optical signal that is DC-free modulated. The DC light obtained by the filtering is injected into the reflective optoelectronic device 207. Here, the reflective optoelectronic device 207 has two functions: First, after the DC light is injected into the reflective optoelectronic device 207, the center wavelength outputted by the reflective optoelectronic device 207 is consistent with the center wavelength of the first downstream optical signal; The uplink OFDM data information is modulated onto the light by the reflective optoelectronic device 207, while the reflective optoelectronic device 207 amplifies the upstream signal. Here, the modulation idea of the upstream optical signal is consistent with the downlink optical signal, and the signal is modulated to the passband, and a certain frequency interval is set with the baseband. Similarly, the output of the obtained upstream optical signal modulates the spectrum, and the center wavelength is still DC light without signal modulation, and the power is significantly amplified.

In this embodiment, the optical filter 205 includes a first optical filtering sub-module and a second optical filtering sub-module. The first optical filtering sub-module is configured to input another optical path through the second circulator and input the optical filter to filter out the signal spectrum to obtain a third downlink optical signal that is DC-free modulated. The second optical filter submodule Block, another path for dividing the second upstream optical signal into the optical filter to filter out a signal spectrum, thereby obtaining a third uplink optical signal that is DC-free modulated, and the DC-free signal-modulated The three upstream optical signals are input as the local oscillator light of the second downstream optical signal through the second circulator

2x2 coupler.

The second beam splitter 206 is configured to divide the second upstream optical signal into two paths, wherein one input is input to the first circulator 201 and the other input is input to the optical filter 205;

The first circulator 201 is further configured to output the second uplink optical signal into one OLT;

The optical filter 205 is further configured to process another path into which the second uplink optical signal is divided to obtain a third uplink optical signal that is DC-free signal-modulated;

The second circulator 204 is further configured to input the DC signal-free third uplink optical signal as the local oscillator of the second downlink optical signal into the 2x2 coupler 203;

The 2x2 coupler 203 is configured to perform coherent reception on the local oscillators of the second downlink optical signal and the second downlink optical signal.

In the embodiment of the present invention, the optical signal outputted from the reflective optoelectronic device 207 is divided into two paths, one of which is input to the first circulator 201, and is sent to the OLT as an upstream optical signal; the other pass through the optical filter 205 again, and the uplink signal The data information is filtered by the optical filter to obtain an amplified DC optical signal, which is input to the 2x2 coupler 203 through the second circulator 204 as the local oscillator of the second downstream optical signal, and the second downstream optical signal is coherently received.

The advantages of the embodiments of the present invention are as follows: First, the terminal side does not need a costly laser with a precisely adjustable wavelength as the local oscillator laser; second, the wavelength of the local oscillator optical signal is the wavelength of the downstream optical signal, because the downlink is The center wavelength of the optical signal is injected into the reflective optoelectronic device. After being coherent with the second downlink optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the required bandwidth of the subsequent electrical device, and does not require any wavelength control mechanism. Third, the polarization state of the downstream optical signal is transmitted through the ODN and reaches the terminal. , its polarization state is random. A typical coherent receiving structure is a polarization diversity mode in which two sets of identical structures are used to receive two polarization states of an optical signal, respectively. In the present invention, the local oscillator signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the correct coherent reception can be completed without the polarization diversity structure. The device complexity is doubled. Fourth, the reflective optoelectronic device is usually operated in a saturated state. After the reflective optoelectronic device erases the downstream optical signal, the upstream data is modulated onto the reflective optoelectronic device. Here, because the optical signal such as to the reflective optoelectronic device is already unmodulated DC light, there is no need to ask for a reverse The imaging optoelectronic device is saturated (saturation requires a higher injected optical power), and the upstream data can be directly modulated onto the light. The requirement of the optical signal power of the injected reflective optoelectronic device is reduced, and the downlink optical power budget is obviously improved; fifth, a reflective optoelectronic device + optical filter structure, simultaneously completing the generation, amplification and uplink signals of the downlink local oscillator DC light Modulation send function. No additional laser is required as the upstream source. Minimizing the required optical components on the terminal side is extremely cost effective.

Embodiment 3:

Referring to FIG. 3, FIG. 3 is a structural diagram of an OFDM passive optical network system according to an embodiment of the present invention. As shown in FIG. 3, the OFDM passive optical network system may include the following devices:

A terminal comprising the device and the photoelectric converter of FIG. 2, an analog mixer, a sine wave generator, a digital to analog converter, an orthogonal frequency division multiplexing decoder;

The device of Fig. 2 has been described in detail in the second embodiment, and will not be described in the third embodiment.

The photoelectric converter 301 is configured to convert the optical signal output by the 2x2 coupler 203 into an analog signal output to the analog mixer 302;

The analog mixer 302 is configured to process the analog electric signal and a sine wave generated by the sine wave generator 303;

The sine wave generator 303 is configured to generate a sine wave output to the analog mixer 302. The digital-to-analog converter 304 is configured to convert an analog electrical signal output by the analog mixer 302 into a digital electrical signal and output the same Orthogonal Frequency Division Multiplexing Decoder 305;

The Orthogonal Frequency Division Multiplexing Decoder 305 is configured to select a digital electrical signal wave of a specific frequency spectrum. a central office, configured to generate a multi-band OFDM electrical signal, a preset first frequency interval exists between a passband frequency of the multi-band OFDM electrical signal and a baseband frequency; and the multi-band OFDM electrical signal is passed through a modulator Modulating into a downlink optical signal, a predetermined second frequency interval exists between a wavelength of the optical signal of the downstream optical signal and a center wavelength of the laser, where the first frequency interval is equal to the second frequency interval; Outputting to the terminal through a circulator, and receiving an uplink optical signal from the terminal; and dividing a part of the downlink laser as a local oscillator laser of the uplink optical signal to perform coherent reception on the uplink optical signal.

At the same time, the central office side also includes a polarization diversity structure, a photoelectric converter, a digital-to-analog converter, and an orthogonal frequency division multiplexing decoder.

The polarization diversity structure described above is used to modulate a laser to separate a part of the polarization state and the upward light of the local oscillator. The polarization state of the signal is such that the polarization state of the local oscillator laser and the polarization state of the upstream optical signal are identical, thereby achieving coherent reception.

In the embodiment of the present invention, the central office generates a multi-band OFDM electrical signal, and the downlink data information is modulated in a passband, and a certain frequency interval is set between the baseband (DC) and the baseband (DC). Here, each subband can correspond to one terminal, or multiple terminals can share one subband, and subcarrier scheduling in the subband is used to complete broadband allocation. The OFDM electrical signal modulates the signal on the light through the modulator. The modulated spectrum has a certain frequency interval between the wavelength of the signal and the center wavelength of the laser, and the frequency interval is the same as the frequency interval between the passband and the baseband of the electrical domain. The modulated optical signal passes through the circulator and is sent to the ODN. After the splitter, it reaches each ONU.

The first downstream optical signal passes through the first circulator 201 and is divided into two paths, wherein one path is input as the second downstream optical signal to the 2x2 coupler 203; the other path is processed by the second circulator 204 and then input to the optical filter 205, thereby A third downlink optical signal with no signal modulation is obtained. The DC light obtained by the filtering is injected into the reflective optoelectronic device 207. Here, the reflective optoelectronic device 207 has two functions: First, after the DC light is injected into the reflective optoelectronic device 207, the center wavelength outputted by the reflective optoelectronic device 207 is consistent with the center wavelength of the first downstream optical signal; The uplink OFDM data information is modulated onto the light by the reflective optoelectronic device 207, while the reflective optoelectronic device 207 amplifies the upstream signal. The modulation idea of the upstream optical signal is consistent with the downlink optical signal, and the signal is modulated to the passband, and a certain frequency interval is set with the baseband. Similarly, the output of the obtained upstream optical signal modulates the spectrum, and the center wavelength is still DC signal without signal modulation, and the power is significantly amplified.

The optical signal outputted from the reflective optoelectronic device 207 is divided into two paths, one of which is input to the first circulator 201 and sent to the OLT as an upstream optical signal; the other passes through the optical filter 205 again, and the uplink signal data information is just optically filtered. The filter is filtered to obtain an amplified DC optical signal, and the 2x2 coupler 203 is input through the second circulator 204 as the local oscillator of the second downlink signal, and the second downstream optical signal is phased. Dry reception.

In this embodiment, after the uplink optical signal arrives at the OLT and passes through the circulator, since the polarization state is random, a polarization diversity structure is required, and the downlink laser splits a part of the local oscillator laser as an uplink optical signal to perform coherent reception on the uplink data. .

In this embodiment, the following advantages are obtained on the terminal side: First, the terminal side does not need a costly laser with a precisely adjustable wavelength as the local oscillator laser; second, the wavelength of the local oscillator optical signal is the wavelength of the downstream optical signal, because It is obtained by injecting the center wavelength of the downstream optical signal into the reflective optoelectronic device. After being coherent with the second downstream optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the bandwidth required by the subsequent electrical equipment, and does not require any wavelength control mechanism. Third, the polarization state of the downstream optical signal is transmitted through the ODN and reaches the terminal. , its polarization state is random. A typical coherent receiving structure is a polarization diversity mode in which two sets of identical structures are used to receive two polarization states of an optical signal, respectively. In the present invention, the local oscillator signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the correct coherent reception can be completed without the polarization diversity structure. The complexity of the device is doubled. Fourth, the reflective optoelectronic device is usually operated in a saturated state. After the reflective optoelectronic device erases the downstream optical signal, the upstream data is modulated onto the reflective optoelectronic device. Here, since the optical signal such as to the reflective optoelectronic device is already unmodulated DC light, it is not necessary to require the reflective optoelectronic device to be saturated (saturation requires a higher injected optical power), and the upstream data can be directly modulated onto the light. The requirement of the optical signal power of the injected reflective optoelectronic device is reduced, and the downlink optical power budget is obviously improved; fifth, a reflective optoelectronic device + optical filter structure, simultaneously completing the generation, amplification and uplink signals of the downlink local oscillator DC light Modulation send function. No additional laser is required as the upstream source. Minimizing the required optical components on the terminal side is extremely cost effective.

Embodiment 4:

Referring to FIG. 4, FIG. 4 is a structural diagram of another OFDM passive optical network system according to an embodiment of the present invention. As shown in FIG. 4, the coherent reception signal system can include the following devices:

The device of Fig. 2 has been described in detail in the second embodiment, and will not be described in the fourth embodiment.

The photoelectric converter 301 is configured to convert the optical signal output by the 2x2 coupler 203 into an analog electrical signal output to the analog mixer 302; The analog mixer 302 is configured to process the analog electrical signal and a sine wave generated by the sine wave generator 303;

The sine wave generator 303 is configured to generate a sine wave output to the analog mixer 302;

The digital-to-analog converter 304 is configured to convert the analog electrical signal output by the analog mixer 302 into a digital electrical signal and output it to the orthogonal frequency division multiplexing decoder 305;

At the same time, the central office side also includes a photoelectric converter, a digital-to-analog converter, and an orthogonal frequency division multiplexing decoder. The central end of the coherent OFDM passive optical network system further includes: modulating the downlink optical signal into a polarization state of the downlink laser by transmitting the downlink optical signal to the terminal through the circulator, and transmitting the signal through the polarization combiner; Before the downlink laser splits a part of the local oscillator laser as the uplink optical signal to coherently receive the uplink optical signal, the downlink laser is divided into a portion of the local oscillator laser that is an upstream optical signal and passes through the first 90-degree polarization rotator. a 2x2 coupler entering the central office; the terminal further comprising: adding a second 90-degree polarization rotator between the reflective optoelectronic device and the circulator 1 to cause the upward optical signal to reach the polarization combiner The polarization state of the optical signal is perpendicular to the polarization state of the downstream optical signal, such that the upstream optical signal is output from the other port of the polarization combiner to the 2x2 coupler of the central office.

In this embodiment, the downlink data is modulated onto one polarization state of the laser (such as the horizontal polarization direction) and transmitted through the polarization combiner. On the terminal side, a 90-degree polarization rotator is added between the reflective optoelectronic device and the first circulator 201, so that when the upstream optical signal reaches the local polarization combiner, the polarization state is perpendicular to the downlink data, and the polarization combiner is Another port output. The down-going laser also passes through a 90-degree polarization rotator and enters the 2x2 coupler for coherent reception with the upstream optical signal. At this time, the polarization states of the local oscillator and the signal light are known, and the vibration direction is known. There is no need to adopt a polarization diversity structure, which reduces the complexity of the device on the central side. Embodiment 5:

Referring to FIG. 5, FIG. 5 is a structural diagram of another coherent OFDM passive optical network system according to an embodiment of the present invention. The system can include the following devices:

At the same time, the central office side also includes a photoelectric converter, a digital-to-analog converter, and an orthogonal frequency division multiplexing decoder. A coherent OFDM passive optical network system, further comprising a splitter, wherein the central office and the splitter are connected by an optical distribution network, and the terminal and the splitter are connected.

As a preferred embodiment, a coherent OFDM passive optical network system, the terminal and the central office pass a wavelength division multiplexing passive optical network (Wavelength Division Multiplexing PON,

WDM-PON), Hybird TDM-WDM PON or Coherent PON connection.

The PON network based on Splitter has been deployed on a large scale. Any upgrade to the network is best based on this network architecture and smooth upgrade. High-order modulation in the electrical domain, such as M-QAM/OFDM technology Mature, after mass production, realized by ASIC, the cost is extremely competitive. These high-order modulation techniques can effectively compress the signal spectrum, compress high-bandwidth signals, and transmit and receive through low-bandwidth optics, reducing the optical cost of PON. For example, a 2.5G optical system is used to transmit 10 Gbps.

Example 6:

Please refer to FIG. 6. FIG. 6 is a flowchart of a method for coherently receiving signals according to an embodiment of the present invention. As shown in FIG. 6, the coherent reception signal method may include the following steps:

601. Divide the first downlink optical signal that passes through the circulator into two paths, where one channel is used as the second downlink optical signal to input the 2x2 coupler; and the other path is passed through the optical filter to obtain the third downlink of the DC no signal modulation. The optical signal passes through the semiconductor optical amplifier to obtain an amplified DC signal-free third downstream optical signal.

In the embodiment of the present invention, the first downlink optical signal is an optical signal sent by the central office to the terminal. The central office generates a multi-band OFDM electrical signal, and the downlink data information is modulated in the passband, and a certain frequency interval is set between the baseband (DC) and the baseband (DC). Here, each subband can correspond to one terminal, or multiple terminals can share one subband, and subcarrier scheduling in the subband is used to complete broadband allocation. The OFDM electrical signal modulates the signal on the light through the modulator. The modulated spectrum has a certain frequency interval between the wavelength of the signal light and the center wavelength of the laser, and the frequency interval is the same as the frequency interval between the passband and the baseband of the electrical domain. The modulated optical signal passes through the circulator and is sent to the ODN. After the splitter, it reaches each ONU.

At the ONU, after the first downstream optical signal passes through the circulator, it is divided into two paths, wherein one path is used as the second downlink optical signal to input the 2x2 coupler; the other path is passed through the optical filter to obtain the DC no signal modulation. The three downstream optical signals are passed through the semiconductor optical amplifier to obtain an amplified DC non-signal modulated third downstream optical signal. The filter is an optical bandpass filter, the center wavelength is the center wavelength of the downstream laser, and the bandwidth is only allowed to pass through the baseband DC component. Because a part of the energy of the first downlink optical signal is distributed at the center wavelength of the signalless modulation (the central unmodulated DC optical carrier is 25 dB larger than the signal frequency band), after passing through the optical filter, the spectral components of the signal are filtered out, and DC is obtained. That is, continuous) optical signals without signal modulation. Such an optical signal conforms to the local oscillator condition as a coherent reception.

In this embodiment, the semiconductor optical amplifier has two functions here: First, after the DC light is injected into the semiconductor optical amplifier, the center wavelength of the semiconductor optical amplifier output is consistent with the central light wavelength of the first downstream optical signal; The semiconductor optical amplifier amplifies the DC unmodulated downstream optical signal.

602. Divide the third downlink optical signal of the amplified DC signalless signal into two according to a certain ratio. a path, wherein a local oscillator as a second downstream optical signal is input to the 2x2 coupler, and the 2x2 coupler performs coherent reception on the local oscillator of the second downstream optical signal and the second downstream optical signal ; Input the other input to the modulator to obtain the second upstream optical signal.

As a preferred embodiment, the amplified DC signal-free third downlink optical signal is divided into two paths in a ratio of 1:9, wherein one tenth of the amplified DC-free signal is modulated. The third downstream optical signal is used as a local oscillator optical input 2x2 coupler of the second downlink optical signal, and the local oscillator light of the second downlink optical signal and the second downlink optical signal is coherently received by the 2x2 coupler; Nine out of ten of the amplified DC signal-free third downstream optical signals are input to the modulator to obtain a second upstream optical signal.

603. The first uplink optical signal is directly loaded by the modulator to another path of the amplified DC signal-free modulated third downlink signal, so that the second uplink optical signal is obtained and output to the OLT.

The advantages of the embodiments of the present invention are as follows: First, the terminal side does not need a costly laser with a precisely adjustable wavelength as the local oscillator laser; second, the wavelength of the local oscillator optical signal is the wavelength of the downstream optical signal, because the downlink is The center wavelength of the optical signal is injected into the SOA. After coherent with the second downstream optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the bandwidth required by the subsequent electrical equipment, and does not require any wavelength control mechanism. Third, the polarization state of the downstream optical signal is transmitted through the ODN and arrives at the terminal. , its polarization state is random. A typical coherent receiving structure is a polarization diversity mode in which two sets of identical structures are used to separately receive the two polarization states of the optical signal. In the present invention, the local oscillator signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the correct coherent reception can be completed without the polarization diversity structure. The device complexity is doubled. Fourth, an SOA+ optical filter + modulator structure completes the generation of the local oscillator DC light, amplification, and modulation of the uplink signal. No additional laser is required as the upstream source. Minimize the required optical components on the terminal side, which has a cost advantage. Fifth, after the optical filter on the ONU side, only the DC light is amplified by SOA, and then divided into 2 channels, one of which enters the 2x2 coupler as The local oscillator of the downstream optical signal passes through a modulator, and the upstream signal is modulated by the modulator to the optical. This prevents the upstream optical signal from being filtered by the optical filter, and the spectrum utilization rate is higher.

Example 7:

Please refer to FIG. 7. FIG. 7 is a structural diagram of a coherent receiving signal device according to an embodiment of the present invention. As shown in FIG. 7, the coherent receiving signal device may include the following devices:

The circulator 701 is configured to output a first downlink signal to the first beam splitter 702; The first optical splitter 702 is configured to divide the first downlink optical signal into two paths, wherein one path is input as a second downlink optical signal to the 2x2 coupler 706; the other input optical filter 703;

The optical filter 703 is configured to process another path that is divided by the first downlink optical signal to obtain a third downlink optical signal that is DC-free modulated.

a semiconductor optical amplifier 704, configured to: amplify the third downlink optical signal modulated by the DC signal to obtain an amplified DC signal-free third downlink optical signal;

At the ONU, the first downstream optical signal passes through the circulator 701 and is divided into two paths, wherein one path is input as the second downlink optical signal to the 2x2 coupler 706; the other path is passed through the optical filter 703 to obtain the DC no signal. The modulated third downstream optical signal is passed through the semiconductor optical amplifier 704 to obtain an amplified DC non-signal modulated third downstream optical signal. The filter 703 is an optical bandpass filter, the center wavelength is the center wavelength of the downstream laser, and the bandwidth is only allowed to pass through the baseband DC component. Because a part of the energy of the first downlink optical signal is distributed at the center wavelength of the signalless modulation (the central unmodulated DC optical carrier is 25 dB larger than the signal frequency band), after passing through the optical filter, the spectral components of the signal are filtered out to obtain a direct current ( That is, continuous) optical signals without signal modulation. Such an optical signal conforms to the local oscillator condition as a coherent reception.

In this embodiment, the semiconductor optical amplifier 704 has two functions: first, after the DC light is injected into the semiconductor optical amplifier, the center wavelength of the semiconductor optical amplifier output is consistent with the central light wavelength of the first downstream optical signal; The semiconductor optical amplifier amplifies the DC unmodulated downstream optical signal.

The second beam splitter 705 is configured to divide the amplified DC signal-free third downlink optical signal into two paths, wherein a local light that is the second downlink optical signal is input to the 2×2 coupler 706. , another input modulator 707;

The modulator 707 is configured to directly load the first uplink optical signal to another path of the amplified DC signal-free modulated third downlink optical signal to obtain a second uplink optical signal.

The circulator 701 is further configured to output the second uplink optical signal to the OLT; The 2x2 coupler 706 is configured to perform coherent reception on the second down optical signal and the local oscillator light of the second downlink optical signal.

The advantages of the embodiments of the present invention are as follows: First, the terminal side does not need a costly laser with a precisely adjustable wavelength as the local oscillator laser; second, the wavelength of the local oscillator optical signal is the wavelength of the downstream optical signal, because the downlink is The center wavelength of the optical signal is injected into the semiconductor optical amplifier. After being coherent with the second downlink optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the required bandwidth of the subsequent electrical device, and does not require any wavelength control mechanism. Third, the polarization state of the downstream optical signal is transmitted through the ODN and reaches the terminal. , its polarization state is random. A typical coherent receiving structure is a polarization diversity mode in which two sets of identical structures are used to receive two polarization states of an optical signal, respectively. In the present invention, the local oscillator signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the correct coherent reception can be completed without the polarization diversity structure. The device complexity is doubled. Fourth, a semiconductor optical amplifier + optical filter + modulator structure, at the same time complete the generation of the local oscillator DC light, amplification and modulation of the uplink signal transmission function. No additional laser is required as the upstream source. Minimizing the required optical components on the terminal side, which has a cost advantage; Fifth, after the optical filter on the ONU side, the semiconductor optical amplifier is only amplified by the direct current light, and is divided into two paths, one of which enters the 2x2 coupling. As the local oscillator of the downstream optical signal, after the other pass through a modulator, the uplink signal is modulated onto the optical through the modulator, so that the upstream optical signal can be prevented from being filtered by the optical filter, and the spectrum utilization rate is higher.

Example 8:

Referring to FIG. 8, FIG. 8 is a structural diagram of an OFDM passive optical network system according to an embodiment of the present invention. As shown in FIG. 8, the OFDM passive optical network system may include the following devices:

A terminal comprising the device and the photoelectric converter of FIG. 7, an analog mixer, a sine wave generator, a digital to analog converter, an orthogonal frequency division multiplexing decoder;

The device of FIG. 7 has been described in detail in Embodiment 7, and will not be described in the eighth embodiment. The photoelectric converter 801 is configured to convert the optical signal output by the 2x2 coupler 706 into an analog electrical signal output to the analog mixer 802;

The analog mixer 802 is configured to process the analog electrical signal and a sine wave generated by the sine wave generator 803;

The sine wave generator 803 is configured to generate a sine wave output to the analog mixer 802. The digital-to-analog converter 804 is configured to convert an analog electrical signal output by the analog mixer 802 into a digital electrical signal and output the same Orthogonal frequency division multiplexing decoder 805;

The Orthogonal Frequency Division Multiplexing Decoder 805 is configured to select a digital electrical signal wave of a specific frequency spectrum. a central office, configured to generate a multi-band OFDM electrical signal, a preset first frequency interval exists between a passband frequency of the multi-band OFDM electrical signal and a baseband frequency; and the multi-band OFDM electrical signal is passed through a modulator Modulating into a downlink optical signal, a predetermined second frequency interval exists between a wavelength of the optical signal of the downstream optical signal and a center wavelength of the laser, where the first frequency interval is equal to the second frequency interval; Outputting to the terminal through a circulator, and receiving an uplink optical signal from the terminal; and dividing a part of the downlink laser as a local oscillator laser of the uplink optical signal to perform coherent reception on the uplink optical signal.

The polarization diversity structure is used to modulate a portion of the laser as a polarization state of the local oscillator and a polarization state of the ascending optical signal such that the polarization state of the local oscillator laser and the polarization state of the upstream optical signal are identical, thereby achieving coherent reception.

At the ONU, the first downstream optical signal passes through the circulator 701 and is divided into two paths, wherein one path is input as the second downlink optical signal to the 2x2 coupler 706; the other path is passed through the optical filter 703 to obtain the DC no signal. Modulating the third downstream optical signal and passing through the semiconductor optical amplifier 704 to obtain an amplified straight A third downstream optical signal that is signal-free modulated. The filter 703 is an optical bandpass filter, the center wavelength is the center wavelength of the downstream laser, and the bandwidth is only allowed to pass through the baseband DC component. Because a part of the energy of the first downlink optical signal is distributed at the center wavelength of the signalless modulation (the central unmodulated DC optical carrier is 25 dB larger than the signal frequency band), after passing through the optical filter, the spectral components of the signal are filtered out to obtain a direct current ( That is, continuous) optical signals without signal modulation. Such an optical signal conforms to the local oscillator condition as a coherent reception.

The circulator 701 is further configured to output the second uplink optical signal to the OLT;

The 2x2 coupler 706 is configured to perform coherent reception on the local oscillators of the second downlink optical signal and the second downlink optical signal.

The advantages of the embodiments of the present invention are as follows: First, the terminal side does not need a costly laser with a precisely adjustable wavelength as the local oscillator laser; second, the wavelength of the local oscillator optical signal is the wavelength of the downstream optical signal, because the downlink is The center wavelength of the optical signal is injected into the semiconductor optical amplifier. After coherent with the second downstream optical signal, the intermediate frequency optical signal is 0 Hz, which naturally achieves the purpose of minimizing the bandwidth required by the subsequent electrical equipment, and does not require any wavelength control mechanism. Third, the polarization state of the downstream optical signal is transmitted and arrived through the ODN. After the terminal, Its polarization state is random. A typical coherent receiving structure is a polarization diversity mode in which two sets of identical structures are used to receive two polarization states of an optical signal, respectively. In the present invention, the local oscillator signal is extracted in the downlink optical signal, and the polarization state thereof is consistent with the downlink optical signal, and the correct coherent reception can be completed without the polarization diversity structure. The device complexity is doubled. Fourth, a semiconductor optical amplifier + optical filter + modulator structure, at the same time complete the generation of the local oscillator DC light, amplification and modulation of the uplink signal transmission function. No additional laser is required as the upstream source. Minimizing the required optical components on the terminal side, which has a cost advantage; Fifth, after the optical filter on the ONU side, the semiconductor optical amplifier is only amplified by the direct current light, and is divided into two paths, one of which enters the 2x2 coupling. As the local oscillator of the downstream optical signal, after the other pass through a modulator, the uplink signal is modulated onto the optical through the modulator, so that the upstream optical signal can be prevented from being filtered by the optical filter, and the spectrum utilization rate is higher.

Example 9:

Referring to FIG. 9, FIG. 9 is a structural diagram of another OFDM passive optical network system according to an embodiment of the present invention. As shown in FIG. 9, the passive optical network system can include the following devices:

The apparatus of Fig. 7 has been described in detail in the seventh embodiment, and will not be described in the ninth embodiment.

The photoelectric converter 801 is configured to convert the optical signal output by the 2x2 coupler 706 into an analog signal output to the analog mixer 802;

The Orthogonal Frequency Division Multiplexing Decoder 805 is configured to select a digital electrical signal wave of a specific frequency spectrum. a central office, configured to generate a multi-band OFDM electrical signal, a preset first frequency interval exists between a passband frequency of the multi-band OFDM electrical signal and a baseband frequency; and the multi-band OFDM electrical signal is passed through a modulator Modulating into a downlink optical signal, a predetermined second frequency interval exists between a wavelength of the optical signal of the downstream optical signal and a center wavelength of the laser, where the first frequency interval is equal to the second frequency interval; Output to the terminal # through the circulator and receive the upstream optical signal from the terminal; The laser splits a portion of the local oscillator laser as the upstream optical signal to coherently receive the upstream optical signal.

The modulator 707 is configured to directly load the first uplink optical signal into another L of the amplified DC signal-free modulated third downlink optical signal to obtain a second uplink optical signal. The circulator 701 is further configured to output the second uplink optical signal to the OLT;

The central end of the coherent OFDM passive optical network system further includes: modulating the downlink optical signal into a polarization state of the downlink laser by transmitting the downlink optical signal to the terminal through the circulator, and transmitting the signal through the polarization combiner; Before the downlink laser splits a part of the local oscillator laser as the uplink optical signal to coherently receive the uplink optical signal, the downlink laser is divided into a portion of the local oscillator laser that is an upstream optical signal and passes through the first 90-degree polarization rotator. a 2x2 coupler entering the central office; the terminal further comprising: adding a second 90-degree polarization rotator between the reflective optoelectronic device and the circulator 1 to cause the upward optical signal to reach the polarization combiner The polarization state of the optical signal is perpendicular to the polarization state of the downstream optical signal, such that the upstream optical signal is output from the other port of the polarization combiner to the 2x2 coupler of the central office.

In this embodiment, the downlink data is modulated onto one polarization state of the laser (such as the horizontal polarization direction) and transmitted through the polarization combiner. On the terminal side, a 90-degree polarization rotator is added between the reflective optoelectronic device and the first circulator 201, so that when the upstream optical signal reaches the local polarization combiner, the polarization state is perpendicular to the downlink data, and the polarization combiner is Another port output. The down-going laser also passes through a 90-degree polarization rotator and enters the 2x2 coupler for coherent reception with the upstream optical signal. At this time, the local oscillator and signal light are known to be in an oscillating state, and the vibration direction is known. There is no need to use a polarization diversity structure, which reduces the complexity of the central side device.

Example 10:

Referring to FIG. 10, FIG. 10 is a structural diagram of another coherent OFDM passive optical network system according to an embodiment of the present invention. The system can include the following devices:

A terminal comprising the device and the photoelectric converter of FIG. 7, an analog mixer, a sine wave generator, a digital to analog converter, an orthogonal frequency division multiplexing decoder; The device of FIG. 7 has been described in detail in Embodiment 7, and will not be described in the tenth embodiment.

The device of Fig. 7 has been described in detail in Embodiment 7, and will not be described in the eighth embodiment.

A coherent OFDM passive optical network system, further comprising a splitter, wherein the central office and the splitter are connected by an optical distribution network, and the terminal and the splitter are connected.

As a preferred embodiment, a coherent OFDM passive optical network system, where the terminal and the central office are connected by WDM-PON, Hybird TDM-DM PON or Coherent PON. The PON network based on Splitter has been deployed on a large scale. Any upgrade to the network is best based on this network architecture and smooth upgrade. The high-order modulation of the electric domain, such as M-QAM/OFDM technology, is very mature. After mass production, it is realized by ASIC, and the cost is extremely competitive. These high-order modulation techniques can effectively compress the signal spectrum, compress high-bandwidth signals, and transmit and receive through low-bandwidth optics, reducing the optical cost of PON. For example, a 2.5G optical system is used to transmit 10 Gbps.

The above is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications, equivalents, and improvements made within the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

Rights request

1. A coherent signal reception method, characterized in that the method includes:

Receive the first downlink optical signal sent from the central office equipment to the terminal equipment, and divide the first downlink optical signal into two channels, wherein one channel is used as the signal light, and the other channel is used to generate the signal light. Oscillate light to coherently receive the signal light and local oscillation light.

2. The method according to claim 1, characterized in that, the method further includes:

3. The method according to claim 1, characterized in that the first downlink optical signal is divided into two channels, wherein one channel is used as signal light, and the other channel is used to generate the signal light. Local oscillation light specifically includes:

Divide the first downstream optical signal into two channels, one of which is used as the second downstream optical signal input coupler; the other channel is filtered to obtain the third downstream optical signal without DC signal modulation;

Directly load the first uplink optical signal onto the third downlink optical signal modulated by the DC signalless signal, and use the modulated third downlink optical signal as the second uplink optical signal;

Divide the second uplink optical signal into two channels, one of which is output to the central office equipment, and the other channel is filtered to obtain a third uplink optical signal modulated by a DC non-signal, and the DC non-signal modulated The third uplink optical signal is input into the coupler as the local oscillator light of the second downlink optical signal.

4. The method according to claim 3, characterized in that, the method further includes:

The second uplink optical signal is deflected and then input into the central office equipment, so that the deflection state of the deflected second uplink optical signal is perpendicular to the deflection state of the first downlink optical signal.

5. The method according to claim 1, characterized in that the first downlink optical signal is divided into two channels, wherein one channel is used as signal light, and the other channel is used to generate the signal light. Local oscillation light specifically includes:

The first downstream optical signal is divided into two channels, one of which is used as the second downstream optical signal input coupler; the other channel is filtered to obtain the third downstream optical signal modulated by the DC signalless signal, and the amplified DC signalless signal is obtained. The third downstream optical signal modulated by the signal;

Divide the amplified DC signal-free modulated third downstream optical signal into two channels according to a certain proportion, wherein one channel is used as a local oscillator optical input coupler for the second downstream optical signal; and the second uplink optical signal is obtained through the other channel ; The first uplink optical signal is directly loaded onto another path branched from the amplified DC signal-free modulated third downlink signal, and the second uplink optical signal is obtained and output to the central office equipment.

6. The method according to claim 5, characterized in that, the method further includes:

7. A coherent signal receiving device, characterized in that the device includes:

The receiving unit is used to receive the downlink optical signal input from the central office;

The first processing unit is used to divide the first downlink optical signal into two channels, wherein one channel is used as the signal light, and the other channel is used to generate the local oscillator light of the signal light;

A coupler used to coherently receive the signal light and the local oscillator light.

8. The device according to claim 7, characterized in that, the device further includes:

9. The device according to claim 7, wherein the first processing unit specifically includes: a first circulator, configured to output the first downlink optical signal to the first optical splitter;

The first optical splitter is used to divide the first downlink optical signal into two channels, wherein one channel is used as the second downlink optical signal input coupler; the other channel is input into the second circulator;

The second circulator is used to transmit the other path divided into the first downlink optical signal to the optical filter;

The optical filter is used to process the other path divided into the first downlink optical signal to obtain a third downlink optical signal without DC signal modulation;

A reflective semiconductor optical amplifier, used to directly load the first uplink optical signal onto the third downlink optical signal modulated by the DC signal-free signal, and use the modulated third downlink DC signal-free optical signal as the second uplink optical signal. Signal;

A second optical splitter is used to divide the second uplink optical signal into two channels, wherein one channel is input to the first circulator, and the other channel is input to the optical filter;

The first circulator is also used to divide the second uplink optical signal into one channel and output it to the central office equipment;

The optical filter is also used to divide the second uplink optical signal into another channel for processing to obtain a third uplink optical signal without DC signal modulation; The second circulator is further configured to input the DC signal-free modulated third uplink optical signal into the coupler as the local oscillator light of the second downlink optical signal.

10. The device according to claim 9, characterized in that, the device further includes a polarization rotator, the polarization rotator is used to deflect the second uplink optical signal and then input it into the central office equipment, The deflection state of the deflected second uplink optical signal is perpendicular to the deflection state of the first downlink optical signal.

11. The device according to claim 7, wherein the first processing unit specifically includes:

Circulator: used to output the first downlink optical signal to the first optical splitter;

The first optical splitter is used to divide the first downstream optical signal into two channels, wherein one channel is used as the second downstream optical signal input coupler; the other channel is input to the optical filter;

The optical filter is used to process the other branch of the first downlink optical signal to obtain the third downlink optical signal without DC signal modulation;

A semiconductor optical amplifier, used to amplify the third downstream optical signal modulated by DC signalless, so as to obtain the amplified third downstream optical signal modulated by DC signalless;

The second optical splitter is used to divide the amplified DC signal-free modulated third downstream optical signal into two channels, wherein one channel is input into the coupler as the local oscillator light of the second downstream optical signal, and the other channel is input modulator;

The modulator is used to directly load the first uplink optical signal onto another path from which the amplified DC signal-free modulated third downlink optical signal is branched off, so as to obtain the second uplink optical signal;

The circulator is also used to output the second uplink optical signal to the central office equipment.

12. The device according to claim 11, characterized in that, the device further includes a polarization rotator, the polarization rotator is used to deflect the second uplink optical signal and then input it into the central office equipment, The deflection state of the deflected second uplink optical signal is perpendicular to the deflection state of the first downlink optical signal.

13. A central office device, characterized in that it includes the device described in any one of claims 7-12.

14. A terminal device, characterized in that it includes the device according to any one of claims 7-12.

15. A passive optical network system, characterized by comprising the central office equipment as claimed in claim 13 and/or the terminal equipment as claimed in claim 14.