CN109327261B - Light path structure of optical repeater - Google Patents

Abstract

The invention relates to the technical field of optical communication, and provides an optical path structure of an optical repeater. In the structure, a first pump laser group is coupled to a first branch of an uplink direction optical path through a first combiner via pump light output by a first output end of a first coupler, and is coupled to a first branch of a downlink direction optical path through a second combiner via pump light output by a second output end of the first coupler; the second pump laser group is coupled to the second branch of the uplink direction optical path through the third combiner via the pump light output by the first output end of the second coupler, and is coupled to the second branch of the downlink direction optical path through the fourth combiner via the pump light output by the second output end of the second coupler. The invention divides the wavelength channel transmitted in the optical fiber into at least two branches for respective amplification, thereby improving the reliability of the optical repeater.

Description

Light path structure of optical repeater

[ technical field ] A method for producing a semiconductor device

The invention relates to the technical field of optical communication, in particular to an optical path structure of an optical repeater.

[ background of the invention ]

Currently, submarine cables carry 97% of the transoceanic traffic, and failure of submarine cable systems can cause significant economic losses, coupled with the high cost of maintenance of submarine cable systems and maintenance times that can be as high as several weeks, thus placing extremely high demands on the reliability of optical repeaters and submarine cables. Compared with an optical cable on the sea bottom, the optical repeater has a complex internal structure, numerous optical and electrical devices and especially important reliability, and a pump laser in the optical repeater is the device with the highest failure rate. For improving reliability, a pump redundancy protection method is usually adopted in the optical repeater to prevent the communication interruption of the whole network caused by the failure of a single pump laser. Fig. 1 shows a conventional pump redundancy protection method in an optical repeater. Two pump lasers provide pump light to the optical amplification units in the upstream and downstream directions of one fiber pair in the repeater after passing through a 2 x 23 dB coupler. The optical amplification unit in fig. 1 includes an erbium-doped fiber providing optical gain and other passive optical devices such as a gain flattening filter for gain flattening. The optical amplifying unit may have a one-stage or two-stage amplifying structure.

If one pump laser in fig. 1 is powered down or even completely fails, half of the pump light can still be distributed to the erbium-doped fiber in the upstream and downstream fiber lines by virtue of the coupling distribution effect of the coupler on the optical power of the two pump lasers, and although the gain and the output power of the optical amplification unit are reduced, the communication of the whole fiber pair is not completely interrupted. Of course, if the decrease of the pump power or the output signal power can be detected, the output power of the pump laser which is not failed is increased in a feedback control mode, so that the gain and the output power of the amplifier can be kept unchanged, but on the one hand, a complex control circuit and a complex control system are introduced into the repeater, and on the other hand, the overall reliability of the repeater can be reduced; on the other hand, a large margin is required to be left for the pump laser, and the submarine special pump laser without refrigeration is generally low in output power and limited in margin. The more common method at present is to not perform any active control on the pump laser, but to use the self-compensation effect when the optical amplification units in the saturation state are cascaded, that is, in the case that the gain of a certain stage of optical amplification unit is reduced, the optical amplification units in the saturation state of several stages below the link can automatically compensate for part of the lost gain. By utilizing the effect, under the conditions that each span is short, the gain of the optical amplification unit is not high, and the design margin of the system is large enough, the system can still maintain the normal communication service of partial or even all wavelengths.

At present, the power of a refrigeration-free pump laser in the submarine repeater is usually less than 500mW, and considering a part of power margin reserved for improving the reliability of the submarine repeater, the method for redundant protection of 2 pump lasers is only suitable for repeaters with the output power of a single optical fiber less than 21 dBm. As the density of wavelength channels in the optical fiber increases, the requirement for the output power of the repeater increases, and to obtain higher gain and output power, 4 pump lasers are often used, and the method of redundancy protection is shown in fig. 2. In the method, two pump lasers are firstly subjected to power synthesis through a Polarization Beam Combiner (PBC), and then the redundant protection of the pump lasers is realized through a 2 x 2 optical coupler. When a single or 2 pumps fail, the gain and total output power in the upstream and downstream directions will drop, and the gain spectrum will tilt (higher gain for long wavelengths). For a C-band repeater with 21dB gain and a bandwidth of 40nm, under the condition that two pumps fail, the total output power is reduced by about 50%, and the original flat gain spectrum is greatly inclined by 2-3 dB. Although the Optical amplifying unit in a saturation state cascaded with the Optical amplifying unit can compensate part of the loss of gain due to the self-compensation effect, the gain flatness of the whole link and the Optical Signal to Noise Ratio (OSNR) degradation can still be caused, especially in the case of large span and high gain, the failure of 2 or 3 pump lasers can still cause that part of the wavelengths and even most of the wavelengths can not maintain normal communication. In addition, this redundancy protection method has two drawbacks: (1) the pump light power is output through a 2 x 2 coupler to form a single-point fault point, and when the coupler fails, the pump lasers input into two paths of optical fiber amplifiers are simultaneously interrupted to cause the interruption of uplink and downlink optical fiber communication; (2) the PBC used by the 2 pump wave combiners is usually manufactured by a polarization maintaining fiber tapering process, the technical implementation difficulty is high, and in addition, the problems of high coupling loss and high failure rate of the polarization beam combiner exist.

In view of the above, overcoming the drawbacks of the prior art is an urgent problem in the art.

[ summary of the invention ]

The invention aims to solve the technical problems that the failure of a pump laser in the prior art affects all channels, and the signal-to-noise ratio of partial wavelength light is easy to reduce and even communication is interrupted under the conditions of high gain and large span. In addition, all the pump light power is output through the 2 × 2 coupler to form a single-point fault point, and when the coupler fails, the pump lasers input into the two optical fiber amplifiers are simultaneously interrupted, so that the upstream optical fiber communication and the downstream optical fiber communication are interrupted.

The invention adopts the following technical scheme:

the invention provides an optical relay optical path structure, which comprises an uplink optical path, a downlink optical path, at least two groups of pump lasers and couplers corresponding to the number of the pump laser groups, wherein the uplink optical path and the downlink optical path respectively comprise at least two branches, and specifically:

the first pump laser group is coupled to a first branch of an uplink direction optical path through a first combiner via pump light output by a first output end of a first coupler; the first pump laser group is coupled to a first branch of the downlink direction optical path through a second combiner via pump light output by a second output end of the first coupler;

the second pump laser group is coupled to a second branch of the uplink direction optical path through a third combiner via pump light output by a first output end of a second coupler; the second pump laser group is coupled to a second branch of the optical path in the downlink direction through a fourth multiplexer via pump light output by a second output end of the second coupler;

a first optical amplification unit and a second optical amplification unit are respectively arranged on a first branch and a second branch of the uplink direction optical path; the first branch and the second branch of the downlink direction optical path are respectively provided with a third optical amplification unit and a fourth optical amplification unit;

and each pump light is coupled to the corresponding branch circuit through the corresponding wave combiner and then enters the light amplification unit on the corresponding branch circuit.

Preferably, the uplink optical path includes a first input signal wave splitter and a first output signal wave combiner, where an input end of the first input signal wave splitter is connected to a trunk on one side of the uplink optical path, an output end of the first output signal wave combiner is connected to a trunk on the other side of the uplink optical path, and a working interval of an optical fiber pair in the repeater is formed between the first input signal wave splitter and the first output signal wave combiner;

at least two output ends of the first input signal wave splitter are respectively connected with a first branch of the uplink direction optical path and a second branch of the uplink direction optical path and are used for splitting an optical signal transmitted on a trunk of the uplink direction optical path into at least two groups of sub-signals, wherein the first group of sub-signals of the uplink direction optical path and the second group of sub-signals of the uplink direction optical path are respectively transmitted through the first branch of the uplink direction optical path and the second branch of the uplink direction optical path;

and the output ends of the first branch of the uplink direction optical path and the second branch of the uplink direction optical path are respectively connected with the input end of the first output signal wave combiner.

Preferably, the first input signal splitter and the first output signal combiner are specifically an input comb filter and an output comb filter, and the first group of sub-signals of the uplink optical path and the second group of sub-signals of the uplink optical path are respectively a wavelength band formed by odd-numbered channel wavelengths and a wavelength band formed by even-numbered channel wavelengths split according to the trunk signal of the uplink optical path.

Preferably, the first input signal wave splitter and the first output signal wave combiner are specifically an input end sub-band filter and an output end sub-band filter, and the first group of sub-signals of the uplink optical path and the second group of sub-signals of the uplink optical path are respectively a first preset wavelength group and a second preset wavelength group, wherein the wavelength of the first preset wavelength group is within an amplifiable wavelength range of the optical amplification unit on the corresponding branch; the wavelength of the second preset wavelength group is within the amplifiable wavelength range of the optical amplification unit on the corresponding branch.

Preferably, the downlink optical path includes a second input signal wave separator and a second output signal wave separator, wherein an input end of the second input signal wave separator is connected to a trunk on one side of the downlink optical path, an output end of the second output signal wave separator is connected to a trunk on the other side of the downlink optical path, and a working interval of the repeater is formed between the second input signal wave separator and the second output signal wave separator;

at least two output ends of the second input signal wave splitter are respectively connected with the first branch of the downlink direction optical path and the second branch of the downlink direction optical path and are used for splitting an optical signal transmitted on the trunk of the downlink direction optical path into at least two groups of sub-signals, wherein the first group of sub-signals of the downlink direction optical path and the second group of sub-signals of the downlink direction optical path are respectively transmitted through the first branch of the downlink direction optical path and the second branch of the downlink direction optical path;

and the output ends of the first branch of the downlink direction optical path and the second branch of the downlink direction optical path are respectively connected with the input end of the second output signal wave combiner.

Preferably, the second input signal splitter and the second output signal combiner are specifically an input comb filter and an output comb filter, and the first group of sub-signals of the downlink optical path and the second group of sub-signals of the downlink optical path are respectively a wavelength band formed by odd-numbered channel wavelengths and a wavelength band formed by even-numbered channel wavelengths split according to the trunk signal of the downlink optical path.

Preferably, the second input signal wave splitter and the second output signal wave combiner are specifically an input end sub-band filter and an output end sub-band filter, and the first group of sub-signals of the downlink optical path and the second group of sub-signals of the downlink optical path are respectively a first preset wavelength group and a second preset wavelength group, wherein the wavelength of the first preset wavelength group is within the amplifiable wavelength range of the optical amplification unit on the corresponding branch; the wavelength of the second preset wavelength group is within the amplifiable wavelength range of the optical amplification unit on the corresponding branch.

Preferably, each of the first optical amplification unit, the second optical amplification unit, the third optical amplification unit, and the fourth optical amplification unit includes an erbium-doped fiber for providing optical gain and/or a gain flattening filter for gain flattening.

Preferably, when each pump laser group is composed of two pump lasers, the combiner is embodied as a 2 × 2 coupler, and is configured to couple one or two signals of the two pump lasers into the 2 × 2 coupler, and input pump lasers to the respective coupled branches through two output ports of the 2 × 2 coupler.

Preferably, in the upward direction light path and the downward direction light path, corresponding to the input end and the output end of the light path structure of the optical repeater, an input optical isolator and an output optical isolator are further respectively provided, specifically:

the input optical isolator is used for inhibiting the reversely amplified spontaneous emission of the optical amplification unit from being transmitted into the optical fiber;

the output optical isolator is used for preventing feedback light on the optical fiber line from generating extra noise and/or lasing in the amplifying unit.

The wavelength channel transmitted in the optical fiber is divided into at least two branches for respective amplification, so that when one or a group of pump lasers corresponding to one branch fails, at least half of the upstream or downstream wavelength channels can be amplified and transmitted without being affected completely, the defect that each channel is affected by the failure of the pump lasers in the traditional 4-pump redundancy protection method is avoided, the risk that the upstream and downstream channels are completely interrupted due to the failure of a key 2 x 2 coupler in the traditional 4-pump redundancy protection method is avoided, and the reliability of the optical repeater is improved.

In a preferred implementation of the present invention, the 4 pump lasers are divided into two groups, each group provides pump light for odd and even channels in the uplink and downlink directions, and the 2 pump lasers in each group are redundant to each other through a 2 × 23 dB coupler.

[ description of the drawings ]

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

FIG. 1 is a schematic diagram of 2-pump redundancy protection in a prior art optical repeater;

FIG. 2 is a schematic diagram of 4-pump redundancy protection in a conventional optical repeater of the prior art;

fig. 3 is a schematic diagram of an optical path structure of an optical repeater according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a 4-pump redundancy protection according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a single-stage light amplifying unit according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a dual-stage light amplification unit according to an embodiment of the present invention;

fig. 7 is a schematic diagram of an optical path structure of an optical branching unit with an amplifying function according to a second embodiment of the present invention.

[ detailed description ] embodiments

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

In the description of the present invention, the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are for convenience only to describe the present invention without requiring the present invention to be necessarily constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1:

embodiment 1 of the present invention provides an optical path structure of an optical repeater, as shown in fig. 3, including an uplink optical path 11, a downlink optical path 12, at least two groups of pump lasers (as shown by dashed line frames labeled 13 and 14 in fig. 3), and couplers (as shown by objects labeled 15 and 16 in fig. 3) corresponding to the number of pump laser groups, where the uplink optical path 11 and the downlink optical path each include at least two branches, as shown in fig. 3, the branches of the uplink optical path 11 include a first branch, a second branch, …, and an nth branch; the branches of the downstream optical path 12 include a first branch, a second branch, …, and an nth branch, specifically:

the pump light output by the first pump laser group 13 via the first output end of the first coupler 15 is coupled to the first branch of the uplink optical path 11 through the first combiner 17; the pump light output by the first pump laser group 13 via the second output end of the first coupler 15 is coupled to the first branch of the downstream direction optical path through the second combiner 18;

the second pump laser group 14 is coupled to the second branch of the uplink optical path 11 through the third combiner 19 via the pump light output by the first output end of the second coupler 16; the second pump laser group 14 is coupled to the second branch of the optical path in the downlink direction through the fourth combiner 20 via the pump light output by the second output end of the second coupler 16;

a first optical amplification unit 25 and a second optical amplification unit 26 are respectively arranged on the first branch and the second branch of the uplink direction optical path; the first branch and the second branch of the downlink direction optical path are respectively provided with a third optical amplification unit 27 and a fourth optical amplification unit 28;

and each pump light is coupled to the corresponding branch circuit through the corresponding wave combiner and then enters the light amplification unit on the corresponding branch circuit.

For example, the pump light coupled into the first branch of the uplink optical path 11 by the first pump laser group 13 through the first combiner 17 may enter the first optical amplifying unit 25 through the first branch of the corresponding uplink optical path 11, so as to complete the amplification process of the corresponding first group of sub-signals in the first branch of the uplink optical path 11; the first pump laser group 13 is coupled to the pump light in the first branch of the optical path 12 in the downlink direction through the second combiner 18, and the pump light enters the third optical amplifying unit 27 through the first branch of the optical path 12 in the downlink direction, so as to complete the amplification process of the corresponding first group of sub-signals in the first branch of the optical path 12 in the downlink direction. The second pump laser group 14 is coupled to the pump light in the second branch of the uplink optical path 11 through the third combiner 19, and the pump light enters the second optical amplifying unit 26 through the second branch of the corresponding uplink optical path 11, so as to complete the amplification process of the corresponding second group of sub-signals in the second branch of the uplink optical path 11; the second pump laser group 14 is coupled to the pump light in the second branch of the downstream optical path 12 through the fourth multiplexer 20, and the pump light enters the fourth optical amplifying unit 28 through the second branch of the corresponding downstream optical path 12, so as to complete the amplification process of the corresponding second group of sub-signals in the second branch of the downstream optical path 12.

The embodiment of the invention divides the wavelength channel transmitted in the optical fiber into at least two branches for respective amplification, so that when one or a group of pump lasers corresponding to one branch fails, at least half of the upstream or downstream wavelength channels can be amplified and transmitted without being affected completely, the defect that each channel is affected by the failure of the pump lasers in the traditional 4-pump redundancy protection method is avoided, the risk that the upper and the lower channels are completely interrupted due to the failure of a key 2 x 2 coupler in the traditional 4-pump redundancy protection method is also avoided, and the reliability of the optical repeater is improved.

In the embodiment of the present invention, two alternative implementations are also proposed for the first input signal demultiplexer 21 and the first output signal multiplexer 22, including:

the first scheme is as follows:

the first input signal demultiplexer 21 and the first output signal multiplexer 22 are specifically an input comb filter and an output comb filter. Through the input comb filter, the multi-wavelength channel is divided into odd-numbered and even-numbered channels, and the first group of sub-signals and the second group of sub-signals are respectively a waveband formed by odd-numbered channel wavelengths and a waveband formed by even-numbered channel wavelengths branched from the trunk signal of the uplink optical path 11. And the odd channel wavelength and the even channel wavelength are respectively output through a first branch and a second branch of the uplink optical path. And the output comb filter is used for combining the amplified odd channel wavelength of the first branch and the amplified even channel wavelength of the second branch and outputting the combined wave. The first branch and the second branch may be respectively used for transmitting odd channel wavelengths and even channel wavelengths, or may be respectively used for transmitting even channel wavelengths and technical channel wavelengths, and here, the specific selection of the branch for transmitting corresponding channel wavelengths is not particularly limited.

Scheme II:

the first input signal demultiplexer 21 and the first output signal multiplexer 22 are specifically an input subband filter and an output subband filter (also referred to as an output subband multiplexer), the input subband filter is a three-port device, a trunk multi-wavelength signal is input at a common end of the three-port device, a transmission band signal within a passband range of the three-port device is output at one output end (transmission end), and a reflection band signal is output at the other output end (reflection end). After passing through the input sub-band filter, the transmitted and reflected band signals correspond to the first and second groups of sub-signals, respectively. Wherein the first group of sub-signals is within an amplification wavelength range of an optical amplification unit (e.g., the first optical amplification unit 25 shown in fig. 3) on the corresponding branch; the wavelengths at the second sub-signals are within the amplifiable wavelength range of the optical amplification unit (e.g., the second optical amplification unit 26 shown in fig. 3) on the corresponding branch. The output sub-band filter and the input sub-band filter have the same structure and are used for outputting the amplified first group of sub-signals and the amplified second group of sub-signals from a common end of the output sub-band filter and the amplified second group of sub-signals after combination. The first group of sub-signals and the second group of sub-signals are divided into two groups by taking the middle as a boundary according to the wavelength sequencing in the simplest mode. In practical cases, the dividing manner may be performed according to system design requirements, which is not described herein.

In addition, the second input signal splitter 23 and the second output signal combiner 24 also exist in two similar implementations of the first input signal splitter 21 and the first output signal combiner 22, and are not described herein again.

In combination with the embodiment of the present invention, a specific implementation example is provided, where when each pump laser group is composed of two pump lasers, the combiner (such as the objects marked with 15 and 16 shown in fig. 3) is specifically represented as a 2 × 2 coupler, and is configured to couple one or two signals of the two pump lasers into the 2 × 2 coupler, and input pump lasers to respective coupled branches through two output ports of the 2 × 2 coupler.

In connection with embodiments of the present invention, for an optical signal amplification structure in a repeater, each optical amplification unit (including the objects identified as 25-28 shown in fig. 3) typically includes an erbium doped fiber for providing optical gain and optionally a gain flattening filter and other optical components for gain flattening, with one or two stages of amplification structures.

In combination with the embodiment of the present invention, there is also a preferred implementation scheme, as shown in fig. 5, in the uplink optical path 11 and the downlink optical path 12, an input optical isolator 29 and an output optical isolator 30 are further respectively disposed corresponding to the input end and the output end of the optical path structure of the optical repeater, specifically:

the input optical isolator 29 is used for inhibiting the transmission of the reversely amplified spontaneous emission noise of the optical amplification unit into the optical fiber;

the output optical isolator 30 is used to prevent the feedback light on the fiber line from generating additional noise and/or lasing in the amplification unit.

Example 2:

an embodiment of the present invention provides a pump redundancy protection method based on an optical repeater according to embodiment 1, where a wavelength channel transmitted in an optical fiber is divided into at least two branches for respective amplification, and as shown in fig. 3, the pump redundancy protection method includes a first branch of an uplink optical path 11, a second branch of the uplink optical path 11, …, an nth branch of the uplink optical path 11, a first branch of a downlink optical path 12, a second branch of the downlink optical path 12, …, and an nth branch of the downlink optical path 12. The number of specific branches may be set according to the requirement for reliability and the severity of the working environment (in the embodiment of the present invention, usually, an optical submarine cable is referred to), and in general, for a case where the requirement for reliability is high and/or the working environment is severe, more branches may be set, so as to distribute the signal amplification process to more pump laser groups, so as to reduce the influence on the effective transmission of the entire optical signal when a certain pump laser or a certain group of pump lasers fails.

The number of the pump lasers in each pump laser group can be two, three or even more, and relatively speaking, the larger the number of the pump lasers in each pump laser group is, the more the burst (for example, a certain pump laser fails), the optical signal can still be effectively transmitted and has better robustness, but the same also brings about an increase in cost. Therefore, in the embodiment 3 of the present invention, an implementation of setting two pump lasers in a single pump laser group is adopted.

The optical relay structure provided by the embodiment of the invention can ensure that when one or a group of pump lasers corresponding to one branch fails, at least half of uplink or downlink wavelength channels can be amplified and transmitted without being affected completely, thereby avoiding the defect that each channel is affected by the failure of the pump lasers in the traditional 4-pump redundancy protection method, avoiding the risk that the upper and the lower channels are completely interrupted due to the failure of a key 2 × 2 coupler in the traditional 4-pump redundancy protection method, and improving the reliability of the optical relay.

Example 3:

the embodiment of the present invention provides an example in a specific application scenario based on the optical path structure of the optical repeater described in embodiment 1 and the pump redundancy protection method described in embodiment 2, although in this embodiment, the identified reference numbers are different from those in embodiment 1, the difference in the reference numbers here indicates that the embodiment of the present invention is represented by embodiment 1 in a specific example scenario, and on the other hand, the embodiment of the present invention also represents the upper and lower example relationships derived from the corresponding features in embodiment 1 by the correspondence between the names and the positions of the structures in the drawings. Referring to fig. 4, the optical path structure comprises an upstream optical path 301, a downstream optical path 302, a first pump laser 303, a second pump laser 304, a third pump laser 305, a fourth pump laser 306, and 2 × 23 dB couplers 307 and 308.

The uplink optical path 301 includes: an input optical isolator 308, an input comb filter 309, a combiner 310 in an odd-numbered wavelength channel, an odd-numbered wavelength optical amplification unit 311, a combiner 312 in an even-numbered wavelength channel, an even-numbered wavelength optical amplification unit 313, an output comb filter 314, and an output optical isolator 315.

The downstream direction optical path includes: an input optical isolator 316, an input comb optical filter 317, a combiner 318 in an odd-wavelength channel, an odd-wavelength optical amplification unit 319, a combiner 320 in an even-wavelength channel, an even-wavelength optical amplification unit 321, an output comb filter 322, and an output optical isolator 323.

The first pump laser 303 and the second pump laser 304 are redundant after passing through the coupler 307 to form a first group of pump lasers, and two output ends of the coupler 306 are respectively connected with the combiner 313 of the even wavelength channel in the uplink and the combiner 321 of the even wavelength channel in the downlink to provide pump light for the even wavelength channel in the uplink and the even wavelength channel in the downlink. Equivalently, the third pump laser 305 and the fourth pump laser 306 form a second group of pump lasers, which are redundant with each other via the coupler 308 and then connected to the wave combiners 310 and 318 to provide pump light for odd wavelength channels in the upstream and downstream directions.

In this embodiment, the signal light of the dense wavelength division multiplexing in the uplink direction is divided into two wavelength bands of odd and even wavelengths after passing through the comb optical filter 309, and these two wavelength bands are amplified by the two optical amplification units 311 and 313, and then output after performing odd and even channel multiplexing by the output comb filter 314. The couplers 307 and 308 provide half the pump light power of the first set of pump lasers (consisting of the first pump laser 303 and the second pump laser 304) and the second set of pump lasers (consisting of the first pump laser 305 and the second pump laser 306) for the two amplification units. The input optical isolator 308 is used to suppress the reverse Amplified Spontaneous Emission (ASE) of the optical amplifier from being transmitted into the optical fiber, and the output optical isolator 315 is used to prevent the feedback light on the optical fiber line from generating additional noise or even lasing in the amplification unit.

Except for the opposite signal transmission direction, the optical path in the downstream direction is similar to the optical path in the upstream direction, and the pump light power of the odd-numbered wavelength channel and the even-numbered wavelength channel is half of that of the first group of pump lasers and the second group of pump lasers respectively.

The optical amplifying unit in this embodiment includes passive optical devices such as erbium-doped fiber and Gain Flattening Filter (GFF) for optical amplification, which may be a single-stage amplifying unit shown in fig. 4, or a two-stage amplifying unit shown in fig. 5, or other more complex multi-stage amplifying optical path structures. The single stage amplification unit, which consists of erbium doped fiber 401 and GFF402, provides only low gain and the power loss introduced by the end GFF402 is also large, resulting in low pump efficiency and output power. To provide higher gain and output power, the two-stage amplification unit shown in fig. 6 is used. In fig. 6, after input signal light and pump light pass through a first section of doped fiber 501, the amplified signal light is distributed by a combiner 502 to a signal path including a GFF503 and an isolator 504, while the remaining pump light is transmitted to a combiner 506 through a pump light path 505, and after the signal light and the remaining pump light pass through a second section of erbium-doped fiber 507, the signal light is amplified again and output.

Table 1 shows the results of comparing this embodiment with the conventional 4-pump redundancy protection scheme of fig. 2. The effect of various possible failure conditions of the pump laser on the channel is as follows: (1) if one of the two pump lasers (303 or 304) in the first group of lasers fails, the pump power of the connected upstream and downstream even wavelength channels is halved, the gains of the upstream amplifying unit 311 and the downstream amplifying unit 319 decrease, the output gain spectrum tilts, although the self-compensation effect of the cascade saturated amplifier can partially recover the power of the cascade saturated amplifier in the next stage of amplifier, in the case of high gain and large span (for example, 24dB gain and 120km span), the compensation effect is limited, which leads to the reduction of transmission quality (increase of bit errors), and even a part of wavelength channels with poor OSNR can generate service interruption. Similarly, if one of the second set of lasers fails, the odd wavelength channels in both the upstream and downstream directions will be affected. But no matter which pump laser fails, half of the channels are completely unaffected; (2) if both pump lasers of the first set of pump lasers fail, the even wavelength channels in the upstream and downstream directions will be completely interrupted, but the odd wavelength channels will be completely unaffected. On the contrary, if the second group of pump lasers are completely out of service, the even wavelength channels in the uplink and downlink directions are completely interrupted, and the even wavelength channels are not influenced completely; (3) if 3 pump lasers fail, only half wavelength channels in the uplink and downlink directions can maintain communication, and the transmission quality is reduced; (4) if one of the first group and the second group of pump lasers fails, each amplifying unit can only obtain half of the original pump power, and all wavelength channels are affected.

TABLE 1 comparison of this embodiment with the conventional 4-pump redundancy protection scheme

In the embodiment of the invention, the optical comb filter is introduced to divide wavelength channels transmitted in the optical fiber into odd channels and even channels for amplification respectively, and pump lasers are grouped to provide pump light for the odd channels and the even channels respectively. So that half of the channels are completely unaffected by any failure of any of the 4 pump lasers. When 2 pump lasers fail, the present embodiment has a 50% probability (the same group of lasers are damaged) that half of the channels are not affected at all. Even in the extreme case of complete failure of 3 pump lasers, there is still 50% of the original pump power in the remaining half of the channel, at least to ensure that part of the wavelength remains for normal service. In the conventional 4-pump redundancy protection mode, the pump power in the erbium-doped fiber is only 25% of the original pump power, and under the conditions of large span and high gain, the service of all wavelengths may be completely interrupted. In addition, in the embodiment, the failure of a single 2 × 2 coupler only causes the interruption of half wavelength channels, thereby avoiding the risk that the failure of a critical 2 × 2 coupler in the conventional redundancy protection scheme causes the complete interruption of all channels.

Example 4:

referring to fig. 7, an embodiment of the present invention illustrates an optical repeater in embodiment 1, which can implement the function of an undersea optical add/drop multiplexing branch unit after being simply modified, and can provide the add/drop function of a half-wavelength channel without additionally introducing a splitting and combining device with large insertion loss. When the structure proposed by the embodiment of the present invention is applied to the subsea branching unit, the specific structure is as shown in fig. 7, and includes:

an upstream optical path 601, a downstream optical path 602, a first pump laser 603, a second pump laser 604, a third pump laser 605, a fourth pump laser 606, 2 × 23 dB couplers 607 and 608.

The uplink optical path 601 includes: an input optical isolator 609, an input comb optical filter 610, an odd wavelength drop end 611, an odd wavelength add end 612, an add end optical isolator 613, a combiner 614 in an odd wavelength channel, an odd wavelength optical amplification unit 615, a combiner 616 in an even wavelength channel, an even wavelength optical amplification unit 617, an output comb filter 618, and an output optical isolator 619.

The downstream direction optical path includes: input optical isolator 620, input comb optical filter 621, odd-wavelength drop end 622, odd-wavelength add end 623, add-end optical isolator 624, combiner 625 in the odd-wavelength channel, odd-wavelength optical amplification unit 626, combiner 627 in the even-wavelength channel, even-wavelength optical amplification unit 628, output comb filter 629, and output optical isolator 630.

The first pump laser 603 and the second pump laser 604 are redundant after passing through the coupler 607 to form a first group of pump lasers, and two output ends of the coupler 607 are respectively connected with the combiner 616 of the even wavelength channel in the uplink and the combiner 627 of the even wavelength channel in the downlink to provide pump light for the even wavelength channel in the uplink and the downlink. Similarly, the third pump laser 605 and the fourth pump laser 606 constitute a second group of pump lasers, which are redundant to each other via the coupler 608, and then are connected to the wave combiners 614 and 625 to provide pump light for odd wavelength channels in the upstream and downstream directions.

In this embodiment, the signal light of the dense wavelength division multiplexing in the uplink direction is divided into two wavelength bands of odd wavelengths and even wavelengths after passing through the comb filter 610, the even wavelength channels of the downlink pass through the downlink end 610 and then continue to be transmitted, and the odd wavelength channels of the uplink pass through the uplink end 611, pass through the uplink isolator 613, and then enter the optical amplification unit 615 for amplification. The even wavelength channels that do not need to go up and down and the odd wavelength channels that need to go up are amplified, then combined by the comb filter 618, and output after passing through the output isolator 619. The same method is also adopted by the signal light in the downlink direction to realize the uplink and downlink of half wavelength. The pump redundancy protection method is the same as that in embodiment 1, and is not described again.

In the embodiment of the invention, the optical comb filter is introduced to decompose a plurality of wavelength channels of dense wavelength division multiplexing transmission in the optical fiber into odd channels and even channels, so that the functions of add and drop of half wavelength channels can be simply realized without additionally introducing a wavelength division and multiplexing optical device with larger insertion loss, and the optical comb filter has the functions of a repeater and an optical add and drop multiplexing branching unit.

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

Claims (9)

1. The utility model provides an optical path structure of optical repeater which characterized in that, includes the coupler of ascending direction light path, descending direction light path, at least two sets of pump laser, corresponding pump laser group quantity, wherein, ascending direction light path and descending direction light path are respectively including two at least branches, and are specific:

the first pump laser group is coupled to a first branch of an uplink direction optical path through a first combiner via pump light output by a first output end of a first coupler; the first pump laser group is coupled to a first branch of the downlink direction optical path through a second combiner via pump light output by a second output end of the first coupler;

the second pump laser group is coupled to a second branch of the uplink direction optical path through a third combiner via pump light output by a first output end of a second coupler; the second pump laser group is coupled to a second branch of the optical path in the downlink direction through a fourth multiplexer via pump light output by a second output end of the second coupler;

a first optical amplification unit and a second optical amplification unit are respectively arranged on a first branch and a second branch of the uplink direction optical path; the first branch and the second branch of the downlink direction optical path are respectively provided with a third optical amplification unit and a fourth optical amplification unit;

each pump light is coupled to the corresponding branch through the corresponding wave combiner and then enters the light amplification unit on the corresponding branch;

the uplink direction optical path comprises a first input signal wave separator and a first output signal wave separator, wherein the input end of the first input signal wave separator is connected with one side trunk of the uplink direction optical path, the output end of the first output signal wave separator is connected with the other side trunk of the uplink direction optical path, and a working interval of the repeater is formed between the first input signal wave separator and the first output signal wave separator;

at least two output ends of the first input signal wave splitter are respectively connected with a first branch of the uplink direction optical path and a second branch of the uplink direction optical path and are used for splitting an optical signal transmitted on a trunk of the uplink direction optical path into at least two groups of sub-signals, wherein the first group of sub-signals of the uplink direction optical path and the second group of sub-signals of the uplink direction optical path are respectively transmitted through the first branch of the uplink direction optical path and the second branch of the uplink direction optical path;

and the output ends of the first branch of the uplink direction optical path and the second branch of the uplink direction optical path are respectively connected with the input end of the first output signal wave combiner.

2. The optical path structure of an optical repeater according to claim 1, wherein the first input signal splitter and the first output signal combiner, specifically an input comb filter and an output comb filter, are respectively a wavelength band formed by odd-numbered channel wavelengths and a wavelength band formed by even-numbered channel wavelengths, which are split according to the main path signal of the uplink optical path, of the first group of sub-signals of the uplink optical path and the second group of sub-signals of the uplink optical path.

3. The optical path structure of an optical repeater according to claim 1, wherein a first input signal splitter and a first output signal combiner, specifically an input end sub-band filter and an output end sub-band filter, respectively, the first group of sub-signals of the uplink optical path and the second group of sub-signals of the uplink optical path are a first preset wavelength group and a second preset wavelength group, respectively, wherein the wavelengths of the first preset wavelength group are within an amplifiable wavelength range of the optical amplifying unit on the corresponding branch; the wavelength of the second preset wavelength group is within the amplifiable wavelength range of the optical amplification unit on the corresponding branch.

4. The optical path structure of claim 1, wherein the downstream optical path comprises a second input signal splitter and a second output signal combiner, wherein an input end of the second input signal splitter is connected to a trunk on one side of the downstream optical path, an output end of the second output signal combiner is connected to a trunk on the other side of the downstream optical path, and an operating region of an optical fiber pair in the optical repeater is formed between the second input signal splitter and the second output signal combiner;

at least two output ends of the second input signal wave splitter are respectively connected with the first branch of the downlink direction optical path and the second branch of the downlink direction optical path and are used for splitting an optical signal transmitted on the trunk of the downlink direction optical path into at least two groups of sub-signals, wherein the first group of sub-signals of the downlink direction optical path and the second group of sub-signals of the downlink direction optical path are respectively transmitted through the first branch of the downlink direction optical path and the second branch of the downlink direction optical path;

and the output ends of the first branch of the downlink direction optical path and the second branch of the downlink direction optical path are respectively connected with the input end of the second output signal wave combiner.

5. The optical path structure of an optical repeater according to claim 4, wherein the second input signal splitter and the second output signal combiner are specifically an input comb filter and an output comb filter, and the first group of sub-signals of the downlink optical path and the second group of sub-signals of the downlink optical path are respectively a wavelength band formed by odd channel wavelengths and a wavelength band formed by even channel wavelengths split according to the trunk signal of the downlink optical path.

6. The optical path structure of the optical repeater according to claim 4, wherein a second input signal splitter and a second output signal combiner, specifically an input terminal sub-band filter and an output terminal sub-band filter, respectively, the first group of sub-signals of the downstream optical path and the second group of sub-signals of the downstream optical path are a first preset wavelength group and a second preset wavelength group, respectively, wherein the wavelengths of the first preset wavelength group are within an amplifiable wavelength range of the optical amplification unit on the corresponding branch; the wavelength of the second preset wavelength group is within the amplifiable wavelength range of the optical amplification unit on the corresponding branch.

7. The optical path structure of an optical repeater according to claim 1, wherein each of the first optical amplification unit, the second optical amplification unit, the third optical amplification unit and the fourth optical amplification unit includes an erbium-doped fiber for providing optical gain and/or a gain flattening filter for gain flattening.

8. The optical circuit structure of claim 1, wherein when each pump laser group is composed of two pump lasers, the combiner is embodied as a 2 × 2 coupler, and is configured to couple one or two signals of the two pump lasers into the 2 × 2 coupler and provide pump light to each coupled branch via two output ports of the 2 × 2 coupler.

9. The optical path structure of an optical repeater according to claim 1, wherein an input optical isolator and an output optical isolator are further respectively disposed in the uplink optical path and the downlink optical path corresponding to the input end and the output end of the optical path structure of the optical repeater, specifically:

the input optical isolator is used for inhibiting the reverse amplified spontaneous emission of the optical amplification unit from being transmitted into the optical fiber;

the output optical isolator is used for preventing feedback light on the optical fiber line from generating extra noise and/or lasing in the amplifying unit.

Images