CN116233658A - Passive optical network system - Google Patents

Passive optical network system Download PDF

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Publication number
CN116233658A
CN116233658A CN202310118820.XA CN202310118820A CN116233658A CN 116233658 A CN116233658 A CN 116233658A CN 202310118820 A CN202310118820 A CN 202310118820A CN 116233658 A CN116233658 A CN 116233658A
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China
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signal
optical network
optical
old
new
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成亮
侯玉兵
沙晶
何培荣
时明
王可为
杨晟
王正洪
范恒
施元元
陈剑胜
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China United Network Communications Group Co Ltd
China Information Technology Designing and Consulting Institute Co Ltd
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China United Network Communications Group Co Ltd
China Information Technology Designing and Consulting Institute Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0075—Wavelength grouping or hierarchical aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0079—Operation or maintenance aspects

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

The disclosure provides a passive optical network system, which relates to access network technology, and includes: a central office and a first optical network system connected by a single-mode fiber; the central office comprises an old optical line terminal, a downlink wavelength complement data transmitter and a first wavelength division multiplexer; the first optical network system comprises a first far-end node, an old optical network unit and a new optical network unit; the old optical line terminal sends an old optical network signal; the downlink wavelength complement data transmitter transmits a new optical network signal and a complement signal; the amplitude of the complement signal is the inverse sum of a plurality of new optical network signals; the first wavelength division multiplexer combines the signals into a target optical network signal; the first remote node divides the target optical network signal into two parts, and part of the target optical network signal is transmitted to the old optical network unit for demodulation and part of the target optical network signal is transmitted to the new optical network unit. The scheme utilizes unused wavelength to carry the complement signal, so that the amplitude of the complement signal is constant after the complement signal is combined with the new optical network signal, and the crosstalk on the old optical network signal is reduced.

Description

Passive optical network system
Technical Field
The present disclosure relates to access network technologies, and in particular, to a passive optical network system.
Background
Passive optical networks (Passive Optical Network, PON) have become the most attractive solution to the access network bottleneck problem. Existing PONs typically provide downstream rates of 1.25Gb/s and 2.5 Gb/s. Due to the rapidly increasing bandwidth demands, upgrading existing PONs to downstream rates of 10Gb/s or higher is a major issue to be addressed.
In the prior art, from an existing PON to a next-generation PON, for example, the next-generation PON may be a time-division multiplexing passive optical network (Time and Wavelength Division Multiplexing Passive Optical Network, TWDM-PON), and a time-division multiplexing technology may be used to increase bandwidth capacity. It is generally considered to add a new-generation PON to an already deployed optical distribution network (Optical Distribution Network, ODN) to reuse existing infrastructure. When a new PON is added, the existing PON is still in use, so the new PON link should coexist with the existing PON link until all existing PON users are upgraded to the new PON link. In order to reduce crosstalk of the new PON signal to the old PON signal, a spectrum shaping line coding technique may be used to apply some line codes to the new PON signal to suppress its low frequency components, thereby achieving reduced crosstalk to the low-speed old PON signal.
However, the spectral shaping line coding technique only works when the bit rate of the old PON signal is much lower than the bit rate of the new PON signal. As the bit rates of the two signals become closer, the crosstalk will increase rapidly. The use effect of the updated PON needs to be further improved.
Disclosure of Invention
The disclosure provides a passive optical network system to solve the problem of large crosstalk between an old PON signal and a new PON signal in the prior art, thereby improving the use effect of the updated PON.
According to a first aspect of the present disclosure, there is provided a passive optical network system comprising:
the central office is connected with the first optical network system through a single-mode fiber; wherein the central office comprises: an old optical line terminal, a downlink wavelength complement data transmitter and a first wavelength division multiplexer; the first optical network system includes: a first remote node, a plurality of old optical network units, a plurality of new optical network units;
the old optical line terminal is used for processing the received first input electric signal, generating and sending an old optical network signal to the first wavelength division multiplexer;
the downstream wavelength complement data transmitter is configured to process the received second input electrical signal, and generate and send a plurality of new optical network signals and a complement signal to the first wavelength division multiplexer; each new optical network signal and the complementary signal have different corresponding wavelengths; the amplitude of the complement signal is the inverse sum of the plurality of new optical network signals;
The first wavelength division multiplexer is configured to combine the old optical network signal, the plurality of new optical network signals, and the complement signal into a target optical network signal; the target optical network signal is transmitted to the first far-end node through the single-mode optical fiber;
the first remote node is configured to divide the target optical network signal into two parts, and transmit one part of the target optical network signal to an old optical network unit for demodulation, so as to obtain and receive a first target signal corresponding to the first input electrical signal; and the other part is transmitted to a new optical network unit for demodulation, so as to obtain and receive a second target signal corresponding to the second input electric signal.
In one implementation, the downstream wavelength complement data transmitter includes M-1 first optical line terminals and 1 second optical line terminal; wherein M is a positive integer greater than 1;
each of the first optical line terminals includes: the first non-return-to-zero coded data end, the first light source and the first optical amplitude modulator; the first non-return-to-zero coded data end is connected with the first end of the first optical amplitude modulator; the first light source is connected with the second end of the first light amplitude modulator; the first non-return-to-zero coded data end is used for processing the received third input electric signal to obtain a first optical signal; the first light source is used for generating a first carrier wave; the first optical amplitude modulator is used for modulating the first optical signal onto the first carrier wave to obtain a new optical network signal;
The second optical line terminal includes: the second non-return-to-zero coded data end, a second light source, a four-level pulse amplitude modulation encoder and a second optical amplitude modulator; the second non-return-to-zero coded data end, the four-level pulse amplitude modulation encoder and the second optical amplitude modulator are sequentially connected; the second light source is connected with the second light amplitude modulator; the second non-return-to-zero coded data end is used for processing the received fourth input electric signal to obtain a second optical signal; the four-level pulse amplitude modulation encoder is used for encoding the second optical signal to obtain a third optical signal; the second light source is used for generating a second carrier wave; the second optical amplitude modulator is used for modulating the third optical signal onto the second carrier wave to obtain a complementary signal.
In one implementation, the old optical line terminal includes: a third non-return-to-zero encoded data end, a third light source, and a third optical amplitude modulator; the third non-return-to-zero encoded data end is connected with the first end of the third optical amplitude modulator; the third light source is connected with the second end of the third light amplitude modulator;
the third non-return-to-zero coded data end is used for processing the received first input electric signal to obtain a fourth optical signal; the third light source is used for generating a third carrier; the third optical amplitude modulator is configured to modulate the fourth optical signal onto the third carrier, to obtain an old optical network signal.
In one implementation, the new optical network unit includes: the optical filter, the first photoelectric detector, the first low-pass filter and the first signal receiver are connected in sequence;
the optical filter is used for filtering the target optical network signal to obtain a fifth optical signal with a required wavelength;
the first photoelectric detector is used for demodulating the detected fifth optical signal to obtain a first electric signal;
the first low-pass filter is used for filtering the first electric signal to obtain a second target signal corresponding to the second input electric signal;
the first signal receiver is configured to receive the second target signal.
In one implementation, the old optical network unit includes: the second photoelectric detector, the second low-pass filter and the second signal receiver are connected in sequence;
the second photoelectric detector is used for demodulating the detected target optical network signal to obtain a second electric signal;
the second low-pass filter is used for filtering the second electric signal to obtain a first target signal corresponding to the first input electric signal;
the signal receiver is configured to receive the first target signal.
In one implementation, the first, second, and third optical amplitude modulators are all mach-zehnder modulators;
and the Mach-Zehnder modulator adopts an amplitude keying modulation mode.
In one implementation, the method further comprises a second wavelength division multiplexer;
the downstream wavelength complement data transmitter, the second wavelength division multiplexer and the first wavelength division multiplexer are sequentially connected; the second wavelength division multiplexer is configured to combine the plurality of new optical network signals and the complement signal into a first optical network signal;
the first wavelength division multiplexer is specifically configured to combine the first optical network signal and the old optical network signal into a target optical network signal.
In one implementation, M is 4.
In one implementation, the first remote node is an optical splitter.
In one implementation, the method further includes: a plurality of second remote nodes, wherein the second remote nodes are used for connecting the remote nodes in the system with old network units or connecting the remote nodes in the system with new optical network units; the second remote node is configured to expand the number of old optical network units or the number of new optical network units in the system.
The passive optical network system provided by the present disclosure includes: the central office is connected with the first optical network system through a single-mode fiber; wherein the central office comprises: an old optical line terminal, a downlink wavelength complement data transmitter and a first wavelength division multiplexer; the first optical network system includes: a first remote node, a plurality of old optical network units, a plurality of new optical network units; the old optical line terminal is used for processing the received first input electric signal, generating and sending an old optical network signal to the first wavelength division multiplexer; the downstream wavelength complement data transmitter is used for processing the received second input electric signal, generating and transmitting a plurality of new optical network signals and a complement signal to the first wavelength division multiplexer; the wavelengths corresponding to the new optical network signals and the complementary code signals are different; the amplitude of the complement signal is the inverse sum of a plurality of new optical network signals; a first wavelength division multiplexer for combining the old optical network signal, the plurality of new optical network signals, and the complement signals into a target optical network signal; transmitting a target optical network signal to a first remote node through a single mode fiber; the first remote node is used for dividing the target optical network signal into two parts, and transmitting one part of the target optical network signal into the old optical network unit for demodulation to obtain and receive a first target signal corresponding to the first input electric signal; and the other part is transmitted to a new optical network unit for demodulation to obtain and receive a second target signal corresponding to the second input electric signal. In the passive optical network system provided by the scheme, the complementary code signals can be carried by utilizing unused wavelengths, so that the amplitude of the complementary code signals is constant after the complementary code signals are combined with the new optical network signals, the crosstalk caused by the combined signals on the old optical network signals is small, and the use effect of the upgraded passive optical network system can be improved.
Drawings
In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present disclosure, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a passive optical network system according to an exemplary embodiment of the present disclosure;
fig. 2 is a schematic diagram illustrating a process of generating a target optical network signal according to an exemplary embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of a passive optical network system according to another exemplary embodiment of the present disclosure;
FIG. 4 is a schematic diagram of a downstream wavelength complement data transmitter according to an exemplary embodiment of the present disclosure;
fig. 5 is a block diagram of a downstream non-return-to-zero coded data transmitter according to an exemplary embodiment of the present disclosure.
Detailed Description
PON has become the most attractive solution to the access network bottleneck problem. Existing PONs typically provide downstream rates of 1.25Gb/s and 2.5 Gb/s. Due to the rapidly increasing bandwidth demands, upgrading existing PONs to downstream rates of 10Gb/s or higher is a major issue to be addressed. The upgrade from an existing PON to a next-generation PON should be smooth because the passive optical network is very cost sensitive, and the cost of the passive optical network comes mainly from building an ODN, and the cost of rebuilding a new ODN is too high, so the new-generation PON is expected to be added to the already deployed ODN to reuse the existing infrastructure. When a new PON is added at the same time, the existing PON is still in use, so the new PON link should coexist with the existing PON link until all existing PON users are upgraded to the new PON link. In view of coexistence, a new PON generally uses a different wavelength from an old PON, and thus a new PON signal and an old PON signal can be separated by an optical filter. When a new PON link is installed, it may be equipped with such a filter. However, old PON links do not have such optical filters because they are not known to need to coexist at deployment time. The cost of adding optical filters in widely distributed optical network units (Optical Network Unit, ONUs) is very high. The added filter is preferably located at the fiber line termination where access may be easier. Therefore, crosstalk in coexistence is crosstalk from a new PON downstream signal to an old PON downstream signal.
In order to eliminate coexistence crosstalk, synchronization pulse interleaving, electric pile modulation, and subcarrier modulation are proposed to provide time/amplitude/frequency domain coexistence of old PON signals and new PON signals in the downstream direction, respectively. However, the proposed method requires expensive devices (such as high-speed photomultipliers and pulse transmitters) or sacrifices the quality of the new PON signal, without further investigation.
One promising technique for smooth upgrades is the spectral shaping line coding technique. Some line codes are applied to the new PON signal to suppress its low frequency components, thereby reducing crosstalk to the low-speed old PON signal. The spectral shaping line coding technique can be operated by software without additional devices. The code may be turned off after the upgrade, so the upgrade is "traceless". Meanwhile, the spectrum shaping line coding technology does not reduce the quality of the new PON downlink signal. The main disadvantage of the spectrally shaped line coding technique is the reduced coding efficiency, and the effective bit rate of the line coded signal is lower than the transmission rate. The spectral shaping line coding technique works only when the bit rate of the old PON signal is much lower than the bit rate of the new PON signal. As the bit rates of the two signals become closer, the crosstalk will increase rapidly.
The amplitude of a new PON signal employing quadrature modulation such as differential phase shift keying, polarization shift keying, and wavelength shift keying is constant, and crosstalk generated to an old PON signal modulated by amplitude shift keying is very small. However, quadrature modulation introduces additional operational complexity, which is not suggested in PON specifications.
In order to solve the technical problem, in the scheme provided by the disclosure, the complementary signal can be carried by using the unused wavelength, so that the amplitude of the complementary signal is constant after being combined with the new optical network signal, and further, the crosstalk caused by the combined signal on the old optical network signal is small, the use effect of the upgraded passive optical network system can be improved, additional operation complexity is not brought, and the implementation is easy.
It should be noted that, the user information (including, but not limited to, user equipment information, user personal information, etc.) and the data (including, but not limited to, data for analysis, stored data, presented data, etc.) related to the present disclosure are information and data authorized by the user or sufficiently authorized by each party, and the collection, use and processing of the related data need to comply with the related laws and regulations and standards of the related country and region, and be provided with corresponding operation entries for the user to select authorization or rejection.
The following describes the technical solutions of the present disclosure and how the technical solutions of the present disclosure solve the above technical problems in detail with specific embodiments. The following embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments. Embodiments of the present disclosure will be described below with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a passive optical network system according to an exemplary embodiment of the present disclosure.
As shown in fig. 1, the passive optical network system provided in this embodiment includes: the central office is connected with the first optical network system through a single-mode fiber; wherein the central office comprises: an old optical line terminal, a downlink wavelength complement data transmitter and a first wavelength division multiplexer; the first optical network system includes: the system comprises a first remote node, a plurality of old optical network units and a plurality of new optical network units.
And the old optical line terminal is used for processing the received first input electric signal, generating and sending the old optical network signal to the first wavelength division multiplexer.
The downstream wavelength complement data transmitter is used for processing the received second input electric signal, generating and transmitting a plurality of new optical network signals and a complement signal to the first wavelength division multiplexer; the wavelengths corresponding to the new optical network signals and the complementary code signals are different; the amplitude of the complement signal is the inverse sum of the plurality of new optical network signals.
A first wavelength division multiplexer for combining the old optical network signal, the plurality of new optical network signals, and the complement signals into a target optical network signal; the target optical network signal is transmitted to the first remote node through a single mode optical fiber.
The first remote node is used for dividing the target optical network signal into two parts, and transmitting one part of the target optical network signal into the old optical network unit for demodulation to obtain and receive a first target signal corresponding to the first input electric signal; and the other part is transmitted to a new optical network unit for demodulation to obtain and receive a second target signal corresponding to the second input electric signal.
Specifically, the passive optical network system may include a central office and a first optical network system connected by a single mode fiber. The central office may include an old optical line terminal, a downstream wavelength complement data transmitter, and a first wavelength division multiplexer. Wherein the first optical network system may include: a first remote node, a plurality of old optical network units, and a plurality of new optical network units. Specifically, the first wavelength division multiplexer is respectively connected with the old optical line terminal, the downlink wavelength complement data transmitter and one end of a single-mode optical fiber, the other end of the single-mode optical fiber is connected with the first end of the first far-end node, and the second end of the first far-end node is respectively connected with a plurality of old optical network units and a plurality of new optical network units.
Specifically, the transmission rate of the old optical network signal sent by the old optical line terminal may be 1.25Gb/s and 2.5Gb/s. Specifically, the transmission speed of the new optical network signal sent by the downlink wavelength complementary code data transmitter can reach 10Gb/s.
Specifically, the old optical line terminal may receive a first input electrical signal that needs to be transmitted, process the received first input electrical signal, and generate and send an old optical network signal to the first wavelength division multiplexer. Wherein, the old optical network signal carries the useful signal which needs to be transmitted.
Specifically, the downstream wavelength complement data transmitter may receive a plurality of second input electrical signals, process the received second input electrical signals, and generate and transmit a plurality of new optical network signals and a complement signal. Wherein the new optical network signal carries a useful signal that needs to be transmitted. The complementary signal does not carry useful signals which need to be transmitted.
Specifically, the wavelengths of the old optical network signal, the plurality of new optical network signals and the complementary code signal are all different. For example, the wavelength of the old optical network signal may be 1490nm; the wavelengths of the plurality of new optical network signals and the complementary code signals can be respectively: 1596.34nm, 1597.19nm, 1598.04nm;1598.89nm.
Specifically, a preset encoding mode may be utilized, so that the amplitude of the complementary signal is the inverse sum of the multiple new optical network signals. Specifically, for example, the amplitude of the complement signal may be [ 3-the sum of the amplitudes of the new optical network signals ]. Thus, the amplitude of the signal when the plurality of new optical network signals are combined with the complement signal is constant. For example, as shown in fig. 2, the plurality of new optical network signals are a new PON signal 1, a new PON signal 2, and a new PON signal 3, respectively; the new PON signal 1 is 01010101; the new PON signal 2 is 00101100; the new PON signal 3 is 01100101; the complement signal is: 31122031; the combined signal (i.e., TWDM-PON combined signal) is 33333333.
Specifically, the first wavelength division multiplexer may combine the old optical network signal, the plurality of new optical network signals, and the complementary signal into the target optical network signal. The generated target optical network signal may then be transmitted into the first optical network system via a single mode optical fiber. As shown in fig. 2, the old optical network signal (i.e., the old PON signal) may be 01; and a combination signal 33333333 of the plurality of new optical network signals and the complementary signal, and the target optical network signal (i.e., the coexistence signal) is obtained after the combination.
Specifically, the target optical network signal may be transmitted to the first remote node through a single mode fiber; the first remote node may downhook a plurality of old optical network units and a plurality of new optical network units. The first remote node may be configured to divide the target optical network signal into multiple parts, transmit a part of the target optical network signal to the old optical network unit for demodulation, obtain and receive a first target signal corresponding to the first input electrical signal, and transmit a part of the target optical network signal to the new optical network unit for demodulation, obtain and receive a second target signal corresponding to the second input electrical signal.
Specifically, the new optical network unit may not need to demodulate and receive the target signal corresponding to the complement signal.
The passive optical network system provided by the present disclosure includes: the central office is connected with the first optical network system through a single-mode fiber; wherein the central office comprises: an old optical line terminal, a downlink wavelength complement data transmitter and a first wavelength division multiplexer; the first optical network system includes: a first remote node, a plurality of old optical network units, a plurality of new optical network units; the old optical line terminal is used for processing the received first input electric signal, generating and sending an old optical network signal to the first wavelength division multiplexer; the downstream wavelength complement data transmitter is used for processing the received second input electric signal, generating and transmitting a plurality of new optical network signals and a complement signal to the first wavelength division multiplexer; the wavelengths corresponding to the new optical network signals and the complementary code signals are different; the amplitude of the complement signal is the inverse sum of a plurality of new optical network signals; a first wavelength division multiplexer for combining the old optical network signal, the plurality of new optical network signals, and the complement signals into a target optical network signal; transmitting a target optical network signal to a first remote node through a single mode fiber; the first remote node is used for dividing the target optical network signal into two parts, and transmitting one part of the target optical network signal into the old optical network unit for demodulation to obtain and receive a first target signal corresponding to the first input electric signal; and the other part is transmitted to a new optical network unit for demodulation to obtain and receive a second target signal corresponding to the second input electric signal. In the passive optical network system provided by the scheme, the complementary code signals can be carried by utilizing unused wavelengths, so that the amplitude of the complementary code signals is constant after the complementary code signals are combined with the new optical network signals, the crosstalk caused by the combined signals on the old optical network signals is small, and the use effect of the upgraded passive optical network system can be improved. And no extra operation complexity is brought, and the method is easy to realize.
Fig. 3 is a schematic structural diagram of a passive optical network system according to another exemplary embodiment of the present disclosure.
Based on the embodiment shown in fig. 1, in the passive optical network system provided in this embodiment, in one implementation manner, the downstream wavelength complement data transmitter (i.e. the TWDM new OLT in fig. 3) includes M-1 first optical line terminals and 1 second optical line terminals; wherein M is a positive integer greater than 1. Each first optical line terminal includes: the first non-return-to-zero coded data end, the first light source and the first optical amplitude modulator; the first non-return-to-zero coded data end is connected with a first end of the first optical amplitude modulator; the first light source is connected with the second end of the first light amplitude modulator; the first non-return-to-zero coded data end is used for processing the received third input electric signal to obtain a first optical signal; the first light source is used for generating a first carrier wave; the first optical amplitude modulator is used for modulating the first optical signal onto a first carrier wave to obtain a new optical network signal.
In one implementation, M is 4.
Specifically, each first optical line terminal may include: a first Non-return-to-zero Code (NRZ) data end, a first light source, and a first optical amplitude modulator. Specifically, the first non-return-to-zero encoded data terminal may be connected to the first terminal of the first optical amplitude modulator; the first light source may be coupled to the second end of the first optical amplitude modulator. Specifically, the first non-return-to-zero encoding data end may be configured to perform non-return-to-zero encoding processing on the received third input electrical signal to obtain a first optical signal; the first light source may be used to generate a first carrier wave; the first optical amplitude modulator may be configured to modulate the first optical signal onto a first carrier to obtain a new optical network signal.
As shown in fig. 3, the wavelengths of the plurality of new optical network signals and the complementary code signals may be respectively: 1596.34nm, 1597.19nm, 1598.04nm;1598.89nm. The new optical network signals may be denoted as new PON signal 1, new PON signal 2, new PON signal 3, respectively. The first light source may be a semiconductor Laser light source (LD).
The third input electrical signal may be a useful signal that requires data transmission.
In one implementation, the first optical amplitude modulator is a Mach-Zehnder modulator (Mach-Zehnder Modulator, MZM); the Mach-Zehnder modulator adopts an amplitude keying modulation mode.
Specifically, the extinction ratio of the Mach-Zehnder modulator may be a common 14dB.
Specifically, the mach-zehnder modulator adopts an amplitude keying modulation mode, which may be a binary amplitude keying modulation mode.
Specifically, the first optical amplitude modulator may be a mach-zehnder modulator; the Mach-Zehnder modulator may employ an amplitude keying modulation scheme. Specifically, the mach-zehnder modulator may modulate the first optical signal onto the first carrier by using an amplitude keying modulation mode, to obtain a new optical network signal.
The second optical line terminal includes: the second non-return-to-zero coded data end, a second light source, a four-level pulse amplitude modulation encoder and a second optical amplitude modulator; the second non-return-to-zero coded data end, the four-level pulse amplitude modulation encoder and the second optical amplitude modulator are sequentially connected; the second light source is connected with the second light amplitude modulator; the second non-return-to-zero coded data end is used for processing the received fourth input electric signal to obtain a second optical signal; the four-level pulse amplitude modulation encoder is used for encoding the second optical signal to obtain a third optical signal; the second light source is used for generating a second carrier wave; the second optical amplitude modulator is used for modulating the third optical signal onto a second carrier wave to obtain a complementary code signal.
Specifically, the second optical line terminal has one more four-level pulse amplitude modulation (4Pulse Amplitude Modulation,PAM4) encoder than the first optical line terminal. Specifically, the second optical line terminal may include: the second non-return-to-zero coded data end, a second light source, a four-level pulse amplitude modulation encoder and a second optical amplitude modulator; and the second non-return-to-zero coded data end, the four-level pulse amplitude modulation encoder and the second optical amplitude modulator are sequentially connected. The second light source is connected to the second optical amplitude modulator. Specifically, the second non-return-to-zero encoding data end may be configured to perform non-return-to-zero encoding processing on the received fourth input electrical signal to obtain a second optical signal; the four-level pulse amplitude modulation coder can be used for carrying out four-level pulse amplitude modulation coding on the second optical signal to obtain a third optical signal; the second light source may be used to generate a second carrier wave; the second optical amplitude modulator is used for modulating the third optical signal onto a second carrier wave to obtain a complementary code signal.
Specifically, PAM4 can generate data through mapping. For example, PAM4 may map bits "00" to "0", "01" to "1", "10" to "2", and "11" to "3".
Wherein the fourth input electrical signal may be a useful signal that is not required for data transmission.
In one implementation, the second optical amplitude modulator is a Mach-Zehnder modulator; the Mach-Zehnder modulator adopts an amplitude keying modulation mode.
Specifically, the second optical amplitude modulator may be a mach-zehnder modulator; the Mach-Zehnder modulator may employ an amplitude keying modulation scheme. Specifically, the mach-zehnder modulator may modulate the third optical signal onto the second carrier by using an amplitude keying modulation mode to obtain the complementary signal.
Specifically, as shown in fig. 2, the new PON signal 1, the new PON signal 2, the new PON signal 3, and the complement signal may constitute a TWDM-PON combined signal. Due to the non-linearity of the MZM modulation, the level distance of the PAM4 signal is not equal, so there is still some ripple with incomplete complement. After transmission over 25km in single mode fiber, the signal is no longer synchronized due to the different dispersion, so the TWDM-PON combined signal no longer has a constant amplitude. Thus, the TWDM-PON combined signal may be pre-delayed to synchronize after transmission such that the TWDM-PON combined signal again becomes nearly constant in amplitude.
In one implementation, the passive optical network system further includes a second wavelength division multiplexer; the downstream wavelength complement data transmitter, the second wavelength division multiplexer and the first wavelength division multiplexer are sequentially connected; the second wavelength division multiplexer is used for combining a plurality of new optical network signals and complementary code signals into a first optical network signal; the first wavelength division multiplexer is specifically configured to combine the first optical network signal and the old optical network signal into a target optical network signal.
Specifically, as shown in fig. 3, the passive optical network system further includes a second wavelength division multiplexer, where the downstream wavelength complement data transmitter, the second wavelength division multiplexer, and the first wavelength division multiplexer are sequentially connected. The second wavelength division multiplexer may be configured to combine the plurality of new optical network signals and the complement signal into a first optical network signal; and then the first optical network signal and the old optical network signal are combined into a target optical network signal by using the first wavelength division multiplexer.
Specifically, as shown in fig. 4, 3 first optical line terminals, 1 second optical line terminal, and a Wavelength Division Multiplexer (WDM) may form a downstream wavelength complement data transmission module. Specifically, wavelengths corresponding to the 3 first optical line terminals and the 1 second optical line terminal may be λ respectively 1 、λ 2 、λ 3 、λ 4 . Each first optical line terminal comprises an optical source, an NRZ data end and a Mach-Zehnder modulator. The second optical line terminal comprises a light source, an NRZ data end, a PAM4 encoder and a Mach-Zehnder modulator.
In one implementation, the old optical line terminal includes: a third non-return-to-zero encoded data end, a third light source, and a third optical amplitude modulator; the third non-return-to-zero coded data end is connected with the first end of the third optical amplitude modulator; the third light source is connected with the second end of the third light amplitude modulator; the third non-return-to-zero coded data end is used for processing the received first input electric signal to obtain a fourth optical signal; the third light source is used for generating a third carrier wave; the third optical amplitude modulator is used for modulating the fourth optical signal onto a third carrier wave to obtain an old optical network signal.
In particular, the old optical line terminal may include a third non-return-to-zero encoded data end, a third optical source, and a third optical amplitude modulator. Wherein the third non-return-to-zero encoded data end is connected to the first end of the third optical amplitude modulator; the third light source is coupled to the second end of the third optical amplitude modulator. Specifically, the third non-return-to-zero encoding data end may be configured to perform non-return-to-zero encoding processing on the received first input electrical signal to obtain a fourth optical signal; the third light source may be for generating a third carrier; the third optical amplitude modulator may be configured to modulate the fourth optical signal onto a third carrier, thereby obtaining an old optical network signal.
In particular, the first input electrical signal may be a useful signal requiring data transmission.
In one implementation, the third optical amplitude modulator is a Mach-Zehnder modulator; the Mach-Zehnder modulator adopts an amplitude keying modulation mode.
Specifically, the third optical amplitude modulator may be a mach-zehnder modulator; the Mach-Zehnder modulator may employ an amplitude keying modulation scheme. Specifically, the mach-zehnder modulator may modulate the fourth optical signal onto the third carrier by using an amplitude keying modulation mode to obtain the complementary signal.
Specifically, as shown in fig. 5, the old optical line terminal (i.e., the old OLT) may also be referred to as a downstream NRZ data transmitter. The old optical line terminal includes an optical source, an NRZ data terminal, and a mach-zehnder modulator.
In one implementation, the first Remote Node (RN) is an optical splitter.
In one implementation, the passive optical network system may further include: a plurality of second remote nodes, the second remote nodes being configured to connect a remote node in the system to an old network element or to connect a remote node in the system to a new optical network element; the second remote node is configured to expand the number of old optical network units or the number of new optical network units in the system.
In particular, the passive optical network system may further comprise a plurality of second remote nodes. Each second remote node may be configured to connect a superior remote node in the system to an old network element or to connect a superior remote node in the system to a new optical network element; the second remote node may be used to expand the number of old optical network units or the number of new optical network units in the system.
Specifically, the second remote node may be the same as the first remote node, and may be an optical splitter.
In one implementation, the new optical network unit includes: the optical filter, the first photoelectric detector, the first low-pass filter and the first signal receiver are connected in sequence; the optical filter is used for filtering the target optical network signal to obtain a fifth optical signal with a required wavelength; the first photoelectric detector is used for demodulating the detected fifth optical signal to obtain a first electric signal; the first low-pass filter is used for filtering the first electric signal to obtain a second target signal corresponding to the second input electric signal; and a first signal receiver for receiving the second target signal.
Specifically, the new optical network unit (i.e. the new ONU) may include: the optical filter, the first photodetector, the first low-pass filter, and the first signal receiver are sequentially connected. The optical filter may be configured to filter the target optical network signal transmitted through the single-mode optical fiber to obtain a fifth optical signal. Specifically, the optical filter may filter out signals with irrelevant wavelengths in the target optical network signal, to obtain a signal with a required wavelength, and further obtain a first optical signal.
The first photodetector may then be used to demodulate the detected fifth optical signal to obtain a first electrical signal. The demodulation scheme in the first photodetector may correspond to the modulation scheme in the mach-zehnder modulator.
The first low pass filter may then be used to filter the first electrical signal to obtain a second target signal corresponding to the second input electrical signal. In particular, the first low-pass filter may be used to filter out low-frequency interference signals in the first electrical signal. The first signal receiver may then be used to receive the second target signal. In particular, a low pass filter may be used to simulate a limited reception bandwidth, and the cut-off frequency may be set to 75% of the received signal bit rate to demodulate the new signal.
In one implementation, the old optical network unit (i.e., old ONU) comprises: the second photoelectric detector, the second low-pass filter and the second signal receiver are connected in sequence. The second photoelectric detector is used for demodulating the detected target optical network signal to obtain a second electric signal; the second low-pass filter is used for filtering the second electric signal to obtain a first target signal corresponding to the first input electric signal; the signal receiver is configured to receive a first target signal.
Specifically, the old optical network unit may include: the second photoelectric detector, the second low-pass filter and the second signal receiver are sequentially connected by using a single-mode fiber. The second photodetector may be configured to demodulate the detected target optical network signal to obtain a second electrical signal. The demodulation scheme in the second photodetector may correspond to the modulation scheme in the mach-zehnder modulator.
The second low pass filter may then be used to filter the second electrical signal to obtain a first target signal corresponding to the first input electrical signal. Specifically, because the bandwidth of the selected second filter is limited, only low-speed signals can be received, and high-speed signals are automatically filtered, the separation of new and old optical network signals in the old optical network unit can be realized. The first target signal may then be received with a signal receiver.
Specifically, the old ONU has no optical filter, and the obtained signal is the new and old signal, but the combination of the new PON signal and the complementary signal can be regarded as direct current, and the crosstalk to the conventional PON signal modulated by the amplitude keying is very small. The complement signal is only to ensure a constant and amplitude of the new PON signal. No PAM is received in any old ONU and therefore no PAM detection is required; new ONUs are able to pick up the corresponding wavelengths due to the presence of optical filters in them.
The wavelength complement employed by the present disclosure may be performed by a software program without the need to add additional equipment. The modulation and demodulation are traditional amplitude keying modulation and demodulation, and modification and complex operation are not needed, so that the upgrading cost is reduced.
In particular, TWDM-PONs may use multiple wavelengths to multiply users and capacity. Typically, as users increase, wavelengths are put into use one after the other, so that the complementary signals can be carried with unused wavelengths to ensure the new PON signal and the amplitude and constancy of the complementary signals. Taking Next Generation passive optical network technology (NG-PON 2) as an example, the NG-PON2 uses four wavelengths, so that an unused wavelength is necessary before the number of users reaches 75% of the maximum number. In the final stage of the upgrade, the number of subscribers in the new PON will exceed 75% and thus the complementary wavelength must be used to carry another new PON signal. In this case, the new PON signal and the old PON signal may be time-division multiplexed (TDM) in time-division multiplexing. If the old PON signal is transmitted, the complementary wavelengths are used to carry the complementary signal to reduce crosstalk to the old PON signal. If the old PON signal is not transmitted, the complementary wavelength is used to carry the new PON signal. In the final stage, most existing ONUs are upgraded, so that the downstream traffic of the old PON becomes very small, and the TDM method is feasible. Such upgrades do not require retrofitting an existing ONU and therefore have no retrofitting costs. All new PON signals are not encoded and thus there is no encoding or decoding process, and the encoding efficiency of each new PON signal is 100%. The complement signal need not be received. When all existing ONUs are upgraded, the complementary wavelength can be used to carry another new PON signal, the upgrade is "traceless".
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It is to be understood that the present disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims (10)

1. A passive optical network system, comprising: the central office is connected with the first optical network system through a single-mode fiber; wherein the central office comprises: an old optical line terminal, a downlink wavelength complement data transmitter and a first wavelength division multiplexer; the first optical network system includes: a first remote node, a plurality of old optical network units, a plurality of new optical network units;
The old optical line terminal is used for processing the received first input electric signal, generating and sending an old optical network signal to the first wavelength division multiplexer;
the downstream wavelength complement data transmitter is configured to process the received second input electrical signal, and generate and send a plurality of new optical network signals and a complement signal to the first wavelength division multiplexer; each new optical network signal and the complementary signal have different corresponding wavelengths; the amplitude of the complement signal is the inverse sum of the plurality of new optical network signals;
the first wavelength division multiplexer is configured to combine the old optical network signal, the plurality of new optical network signals, and the complement signal into a target optical network signal; the target optical network signal is transmitted to the first far-end node through the single-mode optical fiber;
the first remote node is configured to divide the target optical network signal into two parts, and transmit one part of the target optical network signal to an old optical network unit for demodulation, so as to obtain and receive a first target signal corresponding to the first input electrical signal; and the other part is transmitted to a new optical network unit for demodulation, so as to obtain and receive a second target signal corresponding to the second input electric signal.
2. The system of claim 1, wherein the downstream wavelength complement data transmitter comprises M-1 first optical line terminals and 1 second optical line terminals; wherein M is a positive integer greater than 1;
each of the first optical line terminals includes: the first non-return-to-zero coded data end, the first light source and the first optical amplitude modulator; the first non-return-to-zero coded data end is connected with the first end of the first optical amplitude modulator; the first light source is connected with the second end of the first light amplitude modulator; the first non-return-to-zero coded data end is used for processing the received third input electric signal to obtain a first optical signal; the first light source is used for generating a first carrier wave; the first optical amplitude modulator is used for modulating the first optical signal onto the first carrier wave to obtain a new optical network signal;
the second optical line terminal includes: the second non-return-to-zero coded data end, a second light source, a four-level pulse amplitude modulation encoder and a second optical amplitude modulator; the second non-return-to-zero coded data end, the four-level pulse amplitude modulation encoder and the second optical amplitude modulator are sequentially connected; the second light source is connected with the second light amplitude modulator; the second non-return-to-zero coded data end is used for processing the received fourth input electric signal to obtain a second optical signal; the four-level pulse amplitude modulation encoder is used for encoding the second optical signal to obtain a third optical signal; the second light source is used for generating a second carrier wave; the second optical amplitude modulator is used for modulating the third optical signal onto the second carrier wave to obtain a complementary signal.
3. The system of claim 2, wherein the old optical line terminal comprises: a third non-return-to-zero encoded data end, a third light source, and a third optical amplitude modulator; the third non-return-to-zero encoded data end is connected with the first end of the third optical amplitude modulator; the third light source is connected with the second end of the third light amplitude modulator;
the third non-return-to-zero coded data end is used for processing the received first input electric signal to obtain a fourth optical signal; the third light source is used for generating a third carrier; the third optical amplitude modulator is configured to modulate the fourth optical signal onto the third carrier, to obtain an old optical network signal.
4. The system according to claim 1, wherein the new optical network unit comprises: the optical filter, the first photoelectric detector, the first low-pass filter and the first signal receiver are connected in sequence;
the optical filter is used for filtering the target optical network signal to obtain a fifth optical signal with a required wavelength;
the first photoelectric detector is used for demodulating the detected fifth optical signal to obtain a first electric signal;
The first low-pass filter is used for filtering the first electric signal to obtain a second target signal corresponding to the second input electric signal;
the first signal receiver is configured to receive the second target signal.
5. The system according to claim 1, wherein the old optical network unit comprises: the second photoelectric detector, the second low-pass filter and the second signal receiver are connected in sequence;
the second photoelectric detector is used for demodulating the detected target optical network signal to obtain a second electric signal;
the second low-pass filter is used for filtering the second electric signal to obtain a first target signal corresponding to the first input electric signal;
the signal receiver is configured to receive the first target signal.
6. The system of claim 3, wherein the first optical amplitude modulator, the second optical amplitude modulator, and the third optical amplitude modulator are each mach-zehnder modulators;
and the Mach-Zehnder modulator adopts an amplitude keying modulation mode.
7. The system of any of claims 1-6, further comprising a second wavelength division multiplexer;
The downstream wavelength complement data transmitter, the second wavelength division multiplexer and the first wavelength division multiplexer are sequentially connected; the second wavelength division multiplexer is configured to combine the plurality of new optical network signals and the complement signal into a first optical network signal;
the first wavelength division multiplexer is specifically configured to combine the first optical network signal and the old optical network signal into a target optical network signal.
8. A system according to any one of claims 2 to 3, wherein M is 4.
9. The system of any of claims 1-6, wherein the first remote node is an optical splitter.
10. The system of any one of claims 1-6, further comprising: a plurality of second remote nodes, wherein the second remote nodes are used for connecting the remote nodes in the system with old network units or connecting the remote nodes in the system with new optical network units; the second remote node is configured to expand the number of old optical network units or the number of new optical network units in the system.
CN202310118820.XA 2023-01-31 2023-01-31 Passive optical network system Pending CN116233658A (en)

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