WO2016172886A1

WO2016172886A1 - Optical splitter, signal transmission method, and passive optical network

Info

Publication number: WO2016172886A1
Application number: PCT/CN2015/077822
Authority: WO
Inventors: 陈聪; 龚健敏; 杨素林
Original assignee: 华为技术有限公司
Priority date: 2015-04-29
Filing date: 2015-04-29
Publication date: 2016-11-03
Also published as: CN106576000B; CN106576000A

Abstract

Disclosed is an optical splitter, comprising a splitter, a reflector, and a photodetector. One extremity of the photodetector is connected to the splitter, while the other extremity is connected to the reflector. A first output end of the optical splitter is coupled to a trunk optical fiber. A second output end of the optical splitter is coupled to the photodetector. The splitter receives first optical signals transmitted by the optical network unit. A certain percentage of the first optical signals are transmitted to the photodetector via the second output end. The photodetector receives the certain percentage of the first optical signals and converts the certain percentage of the first optical signals into electric signals. The reflector receives the second optical signals transmitted by an optical line terminal and reflects the second optical signal back to the optical line terminal via the electric signal converted by the photodetector. Embodiments of the present invention solve the problem of excessive optical signal loss and restricted upload transmission distance and branching ratio found in an existing optical splitter.

Description

Optical splitter, signal transmission method and passive optical network

Technical field

The present invention relates to the field of optical communication technologies, and in particular, to a splitter, a signal transmission method, and a Passive Optical Network (PON).

Background technique

As users' demand for network bandwidth grows, traditional copper broadband access networks face bandwidth bottlenecks, and fiber access networks become strong competitors for next-generation broadband access networks. Passive Optical Network (PON) systems are the most competitive among various fiber access networks.

FIG. 1 is a schematic structural diagram of a conventional PON system. As shown in FIG. 1 , the existing PON system includes: an optical line terminal (OLT) located at a central office, at least one passive optical splitter (POS), and at least one located at the user end. Optical Network Unit (ONU). The direction from the OLT to the ONU is the downlink direction, and the POS is used to divide the downlink signal power from the OLT into multiple signals and send them to at least one ONU in the downlink direction. The direction from the ONU to the OLT is the uplink direction, and the POS is in the uplink direction. The uplink direction transmits the at least one uplink signal from the at least one ONU to the OLT in a time division multiplexing manner.

Existing POSs include the Fused Biconical Taper (FBT) type and the Planar Lightwave Circuit (PLC) type. Taking a 1:2 POS as an example, in the uplink direction, when an optical signal input from one branch is transmitted from the ONU to the OLT, 50% of the optical power is leaked, and only 50% of the optical power can pass. That is 3dB loss. When the splitting ratio is larger, a larger proportion of the optical power will leak out. Therefore, in the upstream direction, a large amount of light is leaked during the transmission of the existing POS, which causes severe optical loss, and the branch ratio cannot be made large. Moreover, the distance of uplink transmission is greatly limited.

Summary of the invention

The embodiment of the invention provides a beam splitter, a signal transmission method and a passive optical network, which realize signal transmission of a long distance large branch than a passive optical network.

In a first aspect, an embodiment of the present invention provides a beam splitter between an optical line terminal and an optical network unit, including an optical splitter, a reflector, and a photodetector. The optical splitter is connected, the other end is connected to the reflector, the first output of the splitter is coupled to the trunk fiber, and the second output is coupled to the photodetector;

The optical splitter is configured to receive a first optical signal sent by the optical network unit, and send a certain proportion of the first optical signal to the photodetector through the second output end;

The photodetector is configured to receive the first optical signal of the certain ratio; convert the first optical signal of the first ratio into an electrical signal;

The reflector is configured to receive a second optical signal sent by the optical line terminal; and reflect the second optical signal back to the optical line terminal by an electrical signal converted by the photodetector, where the second The wavelength of the optical signal is different from the wavelength of the third optical signal used for data communication between the optical line termination and the optical network unit.

In conjunction with the first aspect, in a first possible implementation manner of the first aspect, the reflector drives the reflection peak of the reflector to be shifted by the electrical signal, so that the wavelength of the reflected peak after the offset is The wavelengths of the second optical signals overlap, and the second optical signals are reflected back to the optical line terminals.

In conjunction with the first aspect, in a second possible implementation of the first aspect, the optical splitter comprises a first optical splitter and a second optical splitter, the photodetector comprising a first photodetector And a second photodetector, the first optical splitter being coupled to the first photodetector, the second optical splitter being coupled to the second photodetector, the first photodetector In series with the second photodetector; wherein

The first optical splitter is configured to receive a first optical signal sent by the optical network unit, and send the first optical signal of the first ratio to the first optical probe by using the second output end Transmitting a second proportion of the first optical signal to the second optical splitter;

The first photodetector is configured to convert the first optical signal of the first ratio into a first electrical signal;

The second optical splitter is configured to receive the second optical signal of the second ratio; and send the first optical signal of the third ratio to the second photodetector through the second output end;

The second photodetector is configured to receive the first electrical signal and the first optical signal of the third ratio; convert the first optical signal of the third ratio into a second electrical signal; The first electrical signal and the second electrical signal are sent to the reflector.

In conjunction with the first aspect, or the first possible implementation of the first aspect, or the second possible implementation of the first aspect, in a third possible implementation of the first aspect, the optical component The router is one or a combination of a directional coupler and a star coupler.

In a second aspect, the embodiment of the present invention further provides a method for signal transmission, including:

Receiving a first optical signal sent by the optical network unit; and transmitting a certain proportion of the first optical signal;

Receiving the certain proportion of the first optical signal; converting the first optical signal of the first ratio into an electrical signal;

Receiving a second optical signal transmitted by the optical line terminal; reflecting the second optical signal back to the optical line terminal by the electrical signal, wherein a wavelength of the second optical signal is used for the optical line terminal and the The wavelengths of the third optical signals used for data communication between the optical network units are different.

With reference to the second aspect, in a first possible implementation manner of the second aspect, the reflection peak wavelength of the reflector is driven by the electrical signal to be offset, such that the reflected reflection peak wavelength and the second The wavelengths of the optical signals overlap, and the second optical signals are reflected back to the optical line terminals.

In conjunction with the second aspect, in a second possible implementation of the second aspect, the optical splitter comprises a first optical splitter and a second optical splitter, the photodetector comprising a first photodetector And the second photodetector receives the first optical signal sent by the optical network unit; sending the first optical signal to the photodetector through the second output end includes:

Receiving a first optical signal sent by the optical network unit; transmitting, by the second output end, the first optical signal of the first ratio to the first photodetector; and using a first optical signal of a second ratio Sending to the second optical splitter;

Converting the first optical signal of the first ratio into a first electrical signal;

Receiving the second ratio of the first optical signal; transmitting the third ratio of the first optical signal to the second photodetector through the second output;

Receiving the first electrical signal and the first optical signal of the third ratio; converting the first optical signal of the third ratio into a second electrical signal; and the first electrical signal and the second electrical A signal is sent to the reflector.

In a third aspect, the present invention also provides a passive optical network comprising an optical network unit, an optical line termination, and the above-described optical splitter.

Based on the foregoing technical solution, the optical splitter of the embodiment of the present invention receives a first optical signal sent by the optical network unit, and then sends a certain proportion of the first optical signal to the photodetector through the second output end; A photodetector converts the first optical signal into an electrical signal, the electrical signal being used to drive the reflector to reflect a second optical signal back to an optical line termination, wherein the wave of the second optical signal The wavelength of the third optical signal for data communication sent by the optical line terminal to the optical network unit is different, which overcomes the problem that the optical loss of the existing optical splitter is excessively large, and the uplink transmission distance and the branch ratio are limited.

DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the present invention, Those skilled in the art can also obtain other drawings based on these drawings without paying any creative work.

FIG. 1 is a schematic block diagram of an application scenario according to an embodiment of the present invention;

2 is a schematic block diagram of a splitter of a passive optical network according to an embodiment of the present invention;

FIG. 3 is a schematic block diagram of a passive optical network according to an embodiment of the present disclosure;

FIG. 4 is a schematic block diagram of a passive optical network according to an embodiment of the present disclosure;

FIG. 5 is a schematic block diagram of a passive optical network according to an embodiment of the present disclosure;

FIG. 6 is a schematic block diagram of a passive optical network according to an embodiment of the present disclosure;

FIG. 7 is a flowchart of a method for signal transmission according to an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of the present invention.

FIG. 1 shows a schematic block diagram of an application scenario according to an embodiment of the present invention. Figure 1 shows the general structure of a passive optical network PON system. In general, a passive optical network system includes an optical line termination OLT at the central office, a passive optical splitter for branching/coupling, and a number of optical network units ONU. The POS is in a central position in the PON network and is used for downlink allocation and uplink coupling of optical signal power. It is usually defined as the downstream direction from the OLT to the ONU, and the upstream direction from the ONU to the OLT.

As shown in FIG. 2, FIG. 2 is a splitting device according to an embodiment of the present invention, which is located between an OLT and an ONU. The optical splitting device includes a splitter 201, a photodetector (PD) 202, and Reflector 203, photodetector 202 end and optical splitter 201 is connected, the other end is connected to a reflector 203, the first output of the splitter 201 is coupled to the backbone fiber, and the second output of the splitter 201 is coupled to the photodetector 202. The optical splitter 201 receives the first optical signal sent by the optical network unit, and then sends a certain proportion of the first optical signal to the photodetector 202 through the second output end. The photodetector 202 receives the first ratio of the first optical signal and then converts the first ratio of the first optical signal into an electrical signal. The reflector 203 receives the second optical signal sent by the optical line terminal, and reflects the second optical signal back to the optical line terminal by an electrical signal converted by the photodetector, wherein the second optical signal The wavelength is different from the wavelength of the third optical signal used for data communication between the optical line termination and the optical network unit.

When the ONU sends an uplink optical signal to the OLT, the photodetector 202 detects the upstream optical signal sent by the ONU, and converts the detected upstream optical signal into an electrical signal, which drives the reflection peak wavelength of the reflector 203 to be offset. When the reflection peak wavelength of the reflector 203 is offset to overlap with the wavelength of the second optical signal emitted by the OLT, the second optical signal is reflected to the OLT along the original optical path, and the OLT can receive the second Optical signal. When the ONU does not send an uplink optical signal to the OLT, the second optical signal is not reflected back, and the OLT does not receive the second optical signal. The optical signal transmitted by the ONU is finally transmitted to the OLT through the second optical signal. Thus, the size of the optical signal received by the OLT is independent of the loss of the splitter and is only related to the second optical signal reflected back to the OLT, while the loss on the backbone fiber is much less than the loss of the splitter.

For the OLT side, the OLT transmits a second optical signal, wherein the wavelength of the second optical signal is different from the wavelength of the third optical signal for data communication that the OLT sends to the ONU. Specifically, the second optical signal may be an O-band (wavelength of 1310 nm band) or a C-band (wavelength of 1550 nm band). The optical line terminal does not require high-power pump light, and only needs to add a normal laser. The second optical signal on the OLT side may be wavelength-division multiplexed (WDM) or may be coupled into the main optical path through a circulator.

The number of optical splitters 201 and photodetectors 202 depends on the actual situation.

For having multiple optical splitters and photodetectors, such as two splitters and two photodetectors, one connection is that the first optical splitter is connected to the first photodetector The second optical splitter is connected to the second photodetector, and the first photodetector and the second photodetector are connected in series; wherein the first optical splitter receives the ONU Sending a first optical signal, sending the first optical signal of the first ratio to the first optical through the second output end The electrical detector transmits a second optical signal of the second ratio to the second optical splitter. The first photodetector converts the first ratio of the first optical signal into a first electrical signal. The second optical splitter receives the first optical signal of the second ratio, and transmits the first optical signal of the third ratio to the second photodetector through the second output end. a second photodetector, configured to receive the first electrical signal and the first optical signal of the third ratio, and convert the first optical signal of the third ratio into a second electrical signal, where the first An electrical signal and the second electrical signal are sent to the reflector.

As shown in FIG. 3, the splitter A is the first optical splitter, the splitter B is the second optical splitter, the photodetector A is the first photodetector, and the photodetector B is the second photodetector. The photodetector A is connected in series with the photodetector B. Among them, the circuit where the splitter A, the splitter B, and the reflector are located is the main optical path. The splitter A receives the first optical signal sent by the ONU, and sends the first optical signal of the first ratio to the photodetector A through the second output end, and the first light of the second ratio A signal is sent to the splitter B. The photodetector A converts the first ratio of the first optical signal into a first electrical signal. The splitter B receives the first optical signal of the second ratio, and transmits the first optical signal of the third ratio to the photodetector B through the second output end. The photodetector B receives the first electrical signal and the first optical signal of the third ratio, converts the first optical signal of the third ratio into a second electrical signal, and the first electrical signal and the The second electrical signal is sent to the reflector.

As shown in FIG. 4, a third optical splitter, such as a splitter C, may be further included. The second output of the splitter C is connected to the photodetector B, and may of course be connected to any other one. Photodetector. Among them, the circuit where the splitter A, the splitter B, the splitter C, and the reflector are located is the main optical path. The splitter C receives the first optical signal of the fourth example sent by the splitter B, and then splits the two optical signals, wherein the optical signal of the fifth example is sent to the photodetector B through the second output. The sixth ratio of optical signals is sent to the reflector.

It should be noted that the first ratio, the second ratio, and the like mentioned in the above embodiments are determined according to the splitter parameters of the splitter. For example, for a 2:2 splitter, the first ratio and the second ratio are both equal to 50%, the third ratio and the fourth ratio are equal to 25%, and the fifth ratio and the sixth ratio are equal to 12.5%. For a 4:4 splitter, both the first and second ratios are equal to 25%, the third and fourth ratios are equal to 12.5%, the fifth and sixth ratios are equal to 6.25%, and so on.

It can be understood that the connection relationship between the splitter and the photodetector in the beam splitter is not limited to the examples of FIG. 3 and FIG. 4, and there may be more connections. A photodetector can receive any number of The optical signal output by the splitter. As shown in FIG. 5, taking 1:8 POS as an example, the light output from the second output terminals of the splitters A, B, C, and D is input to the photodetector A, and the second outputs of the splitters E, F, and G are output. The light output from the terminal is input to another photodetector B. The advantages of the connection are as follows: (1) The optical power received by the two photodetectors A and B is relatively uniform, and the electrical signals are relatively close, and the photodetector A Receiving 4/8 (50%) of the upstream optical power, photodetector B receives 3/8 (37.5%), the higher the branch ratio, the closer the photodetector B is to 50%; (2) the use of photodetectors Quantity, reduce costs.

Through the above embodiment, the optical splitter converts the optical signal "leaked" by each splitter into an electrical signal, and the OLT delivers an optical signal different from the optical signal for data communication sent by the OLT to the ONU. The signal is reflected back by the beam splitter. The reflected light signal is equivalent to the optical signal from the ONU to the OLT side. The light intensity reflected back to the optical signal by the optical splitter is much larger than the optical signal that finally reaches the OLT side from the ONU, from the ONU. The optical signal that goes up to the OLT side can be used or ignored. Through the above embodiments, the problem that the optical signal loss of the existing optical splitter is too large, the distance of the uplink transmission, and the splitting ratio are limited is solved.

The following is an example in which the optical splitter is a 2:2 directional coupler as an example.

As shown in Figure 4, each splitter is assumed to be a 2:2 directional coupler, with the first output of each splitter coupled to the backbone fiber and the second output coupled to the PD. Wherein, the circuit of the splitter A, the splitter B, the splitter C and the reflector is the main optical path, and 50% of the optical power of each of the splitters is in the main fiber, and 50% of the optical power is in the second output. Therefore, this is equivalent to collecting 50% of the optical power, that is, 3dB loss, through the structure of the directional coupler to the second output end, and the second output end is connected to the photodetector, and each photodetector is connected by an electrical connection. Go to the reflector of the backbone fiber. Assuming that the optical power of the ONU is 100%, after passing through the splitter A, 50% of the optical power is sent to the splitter B in the trunk fiber, and 50% of the optical power is at the second output. The optical power output from the splitter B to the trunk fiber is 25%, and the 25% optical power is at the second output. The optical power output from the splitter C to the trunk fiber is 12.5%, and 12.5% of the optical power is at the second output, and finally 87.5% of the optical power is converted into an electrical signal. Preferably, the reflector may be a Distributed Bragg Reflector (DBR).

In addition to the above-mentioned optical splitter type as a directional coupler, there are many options, such as a star coupler, or a combination of a directional coupler and a star coupler. Figure 6 is another embodiment of a LPOS-based PON network. This embodiment differs from Figure 4 in that the last segment of the splitter is used. Compared with Figure 4, the Multimode Interference (MMI) star coupler can avoid cross-loss between PLC waveguides, and the size of the LPOS can be much lower than that of the directional coupler type, which is advantageous for miniaturization.

In the above PON network structure, according to different requirements, an ordinary POS may be cascaded in front of or behind the LPOS to form a multi-level splitting structure. LPOS can be cascaded by fiber-optic directional couplers or cascaded by waveguide-type directional couplers. Compared to fiber-optic LPOS, waveguide LPOS size will be smaller and more suitable for making large branch ratios. LPOS.

Based on the embodiment of the present invention, for the existing PON network, no changes are needed to the trunk optical path and the ONU, and only the OLT and the optical splitter need to be upgraded, which is beneficial to the upgrade of the old network.

In a second aspect, based on the foregoing embodiment, as shown in FIG. 7, the embodiment of the present invention further discloses a method for signal transmission, including the following steps:

Step 701: The optical splitter receives the first optical signal sent by the optical network unit, and then sends a certain proportion of the first optical signal to the photodetector through the second output end.

Specifically, when the ONU sends the uplink optical signal to the OLT, the optical splitter receives the first optical signal sent by the ONU, and a certain proportion of the optical signal is sent to the photodetector through the second output end. The ratio is determined according to the split ratio of the splitter. For a 2:2 splitter, 50% of the first optical signal is output to the photodetector through the second output. For a 4:4 splitter, 25% of the first optical signal is output to the photodetector through the second output.

Step 702: The photodetector receives the certain proportion of the first optical signal, and then converts the first ratio of the first optical signal into an electrical signal.

Step 703: The reflector receives the second optical signal sent by the optical line terminal, and reflects the second optical signal back to the optical line terminal by an electrical signal converted by the photodetector, where the second The wavelength of the optical signal is different from the wavelength of the third optical signal employed for data communication between the optical line termination and the optical network unit.

The reflector receives the second optical signal continuously transmitted by the OLT, and a certain proportion of the first optical signal is converted into an electrical signal, and the reflected signal peak wavelength of the photodetector is driven by the electrical signal, and the reflected peak wavelength and the second optical signal after the offset The wavelengths overlap and reflect the received second optical signal back to the OLT.

Through the above embodiment, the optical splitter converts the optical signal "leaked" by each splitter into an electrical signal, and the OLT delivers an optical signal different from the optical signal for data communication sent by the OLT to the ONU. The signal is reflected back by the beam splitter, and the reflected light signal is equivalent to the ONU The optical signal that reaches the OLT side up the uplink, and the light intensity reflected back to the optical signal by the optical splitter is much larger than the optical signal that finally reaches the OLT side from the ONU. The optical signal from the ONU upstream to the OLT side can be used or ignored. Through the above embodiments, the problem that the optical loss of the existing optical splitter is excessively large, and the distance and the branching ratio of the uplink transmission are limited are solved.

The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any equivalent person can be easily conceived within the technical scope of the present invention by any person skilled in the art. Modifications or substitutions are intended to be included within the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

A light splitter is disposed between the optical line terminal and the optical network unit, and is characterized by comprising an optical splitter, a reflector and a photodetector, wherein one end of the photodetector is connected to the optical splitter, and the other end is connected The reflector is coupled, the first output of the splitter is coupled to the backbone fiber, and the second output is coupled to the photodetector;

The optical splitter is configured to receive a first optical signal sent by the optical network unit, and send a certain proportion of the first optical signal to the photodetector through the second output end;

The photodetector is configured to receive the first optical signal of the certain ratio; convert the first optical signal of the first ratio into an electrical signal;

The reflector is configured to receive a second optical signal sent by the optical line terminal; and reflect the second optical signal back to the optical line terminal by an electrical signal converted by the photodetector, where the second The wavelength of the optical signal is different from the wavelength of the third optical signal used for data communication between the optical line termination and the optical network unit.
The optical splitter according to claim 1, wherein said reflector drives said reflector to shift a reflection peak wavelength by said electrical signal such that said shifted reflection peak wavelength and said second light The wavelengths of the signals overlap and the second optical signal is reflected back to the optical line termination.
The optical splitter of claim 1 wherein said optical splitter comprises a first optical splitter and a second optical splitter, said photodetector comprising a first photodetector and a second optoelectronic a detector, the first optical splitter is connected to the first photodetector, the second optical splitter is connected to the second photodetector, the first photodetector and the second optoelectronic Between detectors; among them,

The first optical splitter is configured to receive a first optical signal sent by the optical network unit, and send the first optical signal of the first ratio to the first optical probe by using the second output end Transmitting a second proportion of the first optical signal to the second optical splitter;

The first photodetector is configured to convert the first optical signal of the first ratio into a first electrical signal;

The second optical splitter is configured to receive the second optical signal of the second ratio; and send the first optical signal of the third ratio to the second photodetector through the second output end;

The second photodetector is configured to receive the first electrical signal and the first optical signal of the third ratio; convert the first optical signal of the third ratio into a second electrical signal; First electricity A signal and the second electrical signal are sent to the reflector.
The optical splitter according to any one of claims 1 to 3, wherein the optical splitter is one or a combination of a directional coupler and a star coupler.
A method for signal transmission, comprising:

Receiving a first optical signal sent by the optical network unit; and transmitting a certain proportion of the first optical signal;

Receiving the certain proportion of the first optical signal; converting the first optical signal of the first ratio into an electrical signal;

Receiving a second optical signal transmitted by the optical line terminal; reflecting the second optical signal back to the optical line terminal by the electrical signal, wherein a wavelength of the second optical signal is used for the optical line terminal and the The wavelengths of the third optical signals used for data communication between the optical network units are different.
The method according to claim 5, wherein the reflection peak of the reflector is driven by the electrical signal to be shifted such that the shifted reflection peak overlaps with the wavelength of the second optical signal, The second optical signal is reflected back to the optical line termination.
The method of claim 5 wherein said optical splitter comprises a first optical splitter and a second optical splitter, said photodetector comprising a first photodetector and a second photodetector And receiving the first optical signal sent by the optical network unit; sending the first optical signal to the photodetector through the second output end, specifically:

Receiving a first optical signal sent by the optical network unit; transmitting, by the second output end, the first optical signal of the first ratio to the first photodetector; and using a first optical signal of a second ratio Sending to the second optical splitter;

Converting the first optical signal of the first ratio into a first electrical signal;

Receiving the second ratio of the first optical signal; transmitting the third ratio of the first optical signal to the second photodetector through the second output;

Receiving the first electrical signal and the first optical signal of the third ratio; converting the first optical signal of the third ratio into a second electrical signal; and the first electrical signal and the second electrical A signal is sent to the reflector.
A passive optical network comprising an optical network unit, an optical line termination, and the optical splitter of any of claims 1-4.