CN108512596A - OSNR computational methods for cascading image intensifer communication system and device - Google Patents

Abstract

The invention discloses a kind of OSNR computational methods and device for cascading image intensifer communication system, are related to technical field of optical fiber communication.This method includes：Using the gain coefficient of image intensifers at different levels, each section of optical fiber attenuation, the net gain of image intensifer fiber segments at different levels is calculated；Each channel signal light power at different levels is calculated using the gain slope of signal light power, image intensifer at different levels after channel number, channel spacing, centre frequency Channel Modulation, and in conjunction with net gain；According to every grade of noise of optical amplifier coefficient, binding signal luminous power calculates the equivalent OSNR costs of link；According to input terminal OSNR output end OSNR is calculated in conjunction with equivalent OSNR costs.The device includes net gain computing module, signal light power computing module, equivalent OSNR costs computing module and target OSNR computing modules.The present invention can effectively solve the problems, such as that measurement accuracy is inadequate in traditional OSNR computational methods, unstable, hardware cost is high and complexity is high.

Description

OSNR calculation method and device for cascaded optical amplifier communication system

technical field

The present invention relates to the technical field of optical fiber communication, in particular to an OSNR (Optical Signal Noise Ratio, optical signal-to-noise ratio) calculation method and device for a cascaded optical amplifier communication system.

Background technique

With the rapid development of new Internet services, the number of users and the amount of data are increasing rapidly, and the demand for network capacity and bandwidth is also increasing. The transmission rate of the optical communication backbone network has increased to the order of Tbit/s, and the channel spacing has gradually transitioned from 100GHz to 50GHz or even lower. The complexity of the network continues to increase. In order to provide stable and reliable services, performance detection of signal transmission quality is particularly important. As one of the important parameters reflecting optical layer performance and communication quality, OSNR needs to be detected accurately.

The key to the OSNR detection technology is to correctly measure the signal optical power and noise optical power, or calculate it based on other parameters that have an exact relationship with the OSNR (such as the electrical noise ratio SNR). Traditional OSNR calculation methods mainly include OSA (Optical Spectrum Analysis, spectral analysis) out-of-band interpolation method, polarization zeroing method, and optical delay interferometry.

Among them, the OSA out-of-band interpolation method uses a narrow-band tunable optical filter to scan the spectrum to estimate the OSNR. However, due to the problem of OSA resolution bandwidth, if the DWDM (Dense Wavelength Division Multiplexing) system uses filter, with the increasing number of channels and decreasing channel spacing, the traditional OSA out-of-band interpolation method can no longer estimate OSNR correctly. For the polarization-nulling method, when the signal is depolarized (PMD-Polarization Mode Dispersion, caused by polarization mode dispersion or nonlinear birefringence) or ASE (Amplifiedspontaneous emission, amplified spontaneous emission) noise produces partial polarization (PDL-Polarization DependentLoss, polarization-dependent When caused by loss and PDG-Polarization Dependent Gain), the accuracy of the measurement will be greatly affected. For the optical delay interferometry, it is necessary to introduce a delay line device, which makes the hardware cost high, and it will appear unstable with the environment, which is not easy to observe and operate.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned deficiencies in the background technology, to provide a kind of OSNR calculation method and device for the cascaded optical amplifier communication system, which can effectively solve the problem of insufficient measurement accuracy, instability, high hardware cost and problems in the traditional OSNR calculation method. A problem of high complexity.

In order to achieve the above object, the present invention provides a kind of OSNR calculation method for the cascaded optical amplifier communication system, comprising the following steps: S1, using the gain coefficients of the optical amplifiers at all levels and the attenuation of each section of optical fiber to calculate the optical amplifier at all levels-optical fiber attenuation S2, using the number of channels, the channel spacing, the signal optical power modulated by the center frequency channel, the gain slopes of the optical amplifiers at all levels, and combining the net gains of the optical amplifiers at all levels-optical fiber sections obtained in S1, calculate each The signal optical power of each level of each channel; S3, according to the noise figure of each level of optical amplifier, combined with the signal optical power of each channel and each level obtained in S2, calculate the equivalent OSNR cost of the link; S4, according to the determined input terminal OSNR , combined with the equivalent OSNR cost obtained from S3, to calculate the output OSNR.

On the basis of the above technical solution, after step S2, the following operations are also included: compare the calculated signal optical power of each channel and level with the actual measured optical power, and if the difference between the two exceeds the specified threshold, then determine There is a failure in the link.

On the basis of the above-mentioned technical solution, in step S1, when using the gain coefficients of optical amplifiers at all levels and the attenuation of optical fibers at each section to calculate the net gain of optical amplifiers at all levels-optical fiber sections, the following formula is used to calculate:

Δ _j =G _j *L _j

Among them, Δ _j represents the net gain of the j-level optical amplifier-fiber section, j∈[1,N]; N represents the total number of optical amplifier stages, which is a positive integer greater than 1; G _j represents the gain of the j-level optical amplifier Coefficient, L _j represents the fiber attenuation of the jth segment.

On the basis of the above technical solution, step S2 specifically includes the following operations:

1) Determine the center frequency of the optical amplifier, and use the signal optical power modulated by the center frequency channel Combined with the net gain Δ _j of the optical amplifier-fiber section at all levels calculated in S1, the signal optical power of the center frequency channel in the optical amplifiers at all levels is calculated step by step Its calculation formula is:

Among them, i ₀ represents the center frequency channel number, and j represents the jth level optical amplifier;

2) Determine the number of channels Ch, and use the calculated center frequency channel signal optical power at all levels of optical amplifiers The channel spacing and the gain slopes of optical amplifiers at all levels are used to calculate the signal optical power Pin_e _{(i, j)} of each channel and each level. The calculation formula is:

Among them, i represents the i-th channel, i∈[1, Ch]; GT _j represents the gain slope of the j-level optical amplifier; B represents the channel spacing.

On the basis of the above technical solution, step S3 specifically includes the following operations:

1) Calculate _{k (i, j) according to the noise coefficient of each level of optical amplifier combined with the signal optical power Pin_e (i, j)} of each channel and level obtained in S2, and the k _{( i, j)} is the jth level The influence of the noise characteristics of the optical amplifier on the i-th channel OSNR, its calculation formula is:

Among them, F _j represents the noise figure of the jth optical amplifier;

2) After accumulating the k _{(i, j)} of all levels of optical amplifiers, take the reciprocal, and calculate the equivalent OSNR cost OSNR _link of the entire link. The calculation formula is:

Wherein, N1 represents the N1-level optical amplifier, and N2 represents the N2-level amplifier; when calculating the k _{(i, j)} of the cumulative optical amplifier from the 1st level to the j-th level, then N1=1, N2=j, and thus analogy.

On the basis of the above technical solution, in step S4, according to the determined input terminal OSNR, combined with the equivalent OSNR cost obtained in S3, when calculating the output terminal OSNR, the following formula is used for calculation:

Among them, OSNR _in is the OSNR of the input terminal, OSNR _link is the equivalent OSNR cost obtained by S3, and OSNR _out is the OSNR of the output terminal.

On the basis of the above technical solution, the optical amplifier is an erbium-doped fiber amplifier EDFA.

On the basis of the above technical solution, the cascaded optical amplifier communication system includes a laser light source, an optical modulator, and N cascaded optical amplifiers; the optical modulator is connected to the output end of the laser light source for modulating the laser light source The optical signal sent; the N cascaded optical amplifiers are connected by an optical fiber for transmitting optical signals, and the first-stage optical amplifier is connected to the output end of the optical modulator for modulating the output of the optical modulator The optical signal is amplified and then output, and the Nth-stage optical amplifier is connected to the output end of the optical fiber for amplifying the transmitted optical signal and outputting it.

The present invention also provides an OSNR calculation device for a cascaded optical amplifier communication system that implements the above method, the device includes a net gain calculation module, a signal optical power calculation module, an equivalent OSNR cost calculation module and a target OSNR calculation module;

The net gain calculation module is used to: use the gain coefficients of the optical amplifiers at all levels and the attenuation of each section of optical fiber to calculate the net gain of the optical amplifier-fiber section at all levels;

The signal optical power calculation module is used to: use the number of channels, the channel spacing, the signal optical power modulated by the center frequency channel, the gain slopes of the optical amplifiers at all levels, and combine the optical amplifiers at all levels obtained by the net gain calculation module- The net gain of the fiber segment, calculate the signal optical power of each channel and each level;

The equivalent OSNR cost calculation module is used to: calculate the equivalent OSNR cost of the link according to the noise coefficient of each level of optical amplifier, combined with the signal optical power of each channel and each level obtained by the signal optical power calculation module;

The target OSNR calculation module is configured to: calculate the output terminal OSNR according to the determined input terminal OSNR combined with the equivalent OSNR cost obtained by the equivalent OSNR cost calculation module.

On the basis of the above technical solution, the device also includes a fault detection module, which is used to: compare the signal optical power of each channel and each level calculated by the signal optical power calculation module with the actual measured optical power In contrast, if the difference between the two exceeds the specified threshold, it is determined that there is a fault in the link.

The beneficial effects of the present invention are:

(1) The present invention is based on EDFA link analysis, calculates OSNR by the noise characteristic of optical amplifier and the operating condition of amplification, finds that the OSNR cost in the link is only relevant with the characteristic of optical amplifier and optical fiber, and other devices and other components of transceiver end and The structure is not required and can be calculated independently. Therefore, the present invention only uses parameters such as channel number, channel spacing, modulated signal optical power, gain coefficient, gain slope and noise figure of the optical amplifier to calculate and gradually calculate the output OSNR of the entire link. Compared with the existing technology, the measurement accuracy is high, the stability is good, the hardware cost is low, and the complexity is low, and it has certain significance for the design of the optical transmission system in the future.

(2) After the present invention calculates the signal optical power Pin_e _{(i, j)} of each channel and each level, the calculated Pin_e _{(i, j)} can be compared with the actual measured optical power Pin _{(i, j)} , if the difference between Pin_e _{(i, j)} and Pin _{(i, j)} is too large, it indicates that there is a fault in the link. Through the above operations, it is possible to quickly detect whether there is a fault in the link, which meets the actual use requirements.

(3) The present invention is applicable to various high-speed and flexible optical fiber communication systems, has a wide application range, and can meet the requirements of various application environments.

Description of drawings

Fig. 1 is a structural schematic diagram of a typical cascaded optical amplifier communication system;

FIG. 2 is a flow chart of an OSNR calculation method for a cascaded optical amplifier communication system in an embodiment of the present invention;

FIG. 3 is a structural block diagram of an OSNR computing device used in a cascaded optical amplifier communication system in an embodiment of the present invention;

4 is another structural block diagram of an OSNR calculation device used in a cascaded optical amplifier communication system in an embodiment of the present invention;

Fig. 5 is the schematic diagram of each stage optical amplifier gain and optical fiber link loss in the simulation example;

Fig. 6 is the schematic diagram of the signal optical power of each level channel entering each level of EDFA in the simulation example;

Fig. 7 is the schematic diagram of the reciprocal k of the OSNR cost of EDFA of different channels at all levels in the simulation example;

Figure 8 is a schematic diagram of the calculated OSNR in the simulation example;

FIG. 9 is a schematic diagram of the difference between the OSNR calculated in the simulation example and the OSNR measured in the simulation.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The design idea of the present invention is to provide an OSNR calculation scheme for a cascaded optical amplifier communication system. Wherein, the cascaded optical amplifier communication system, as shown in FIG. 1 , includes a laser light source, an optical modulator, and N cascaded optical amplifiers, where N is a positive integer greater than 1. Wherein, the optical modulator is connected to the output end of the laser light source for modulating the optical signal sent by the laser light source; N cascaded optical amplifiers are connected through optical fibers for transmitting optical signals, and the first-stage optical amplifier is connected to The output end of the optical modulator is used to amplify the modulated optical signal output by the optical modulator and then output it. The Nth-stage optical amplifier is connected to the output end of the optical fiber and is used to amplify the transmitted optical signal and output it.

It can be understood that in a cascaded optical amplifier communication system, such as a cascaded EDFA (Erbium-doped Optical Fiber Amplifier, Erbium-doped Optical Fiber Amplifier) DWDM system, the decline in OSNR performance is mainly caused by the ASE noise accumulated by EDFAs at all levels of. During link transmission, the attenuation of signal optical power will be compensated by the optical amplifier, but the noise will also be compensated. As the number of optical amplifier stages continues to increase, each optical amplifier will introduce new ASE noise, resulting in a continuous decline in OSNR. Therefore, OSNR can be directly obtained by calculating the ratio of the output signal optical power of each optical amplifier to the generated ASE noise power. Among them, the optical power of the output signal is calculated through the optical power of the input signal, the gain of the optical amplifier, and the link loss; while the ASE noise power can be calculated by recursive accumulation step by step along the transmission link.

Based on the above design ideas, the present invention provides an OSNR calculation scheme for a cascaded optical amplifier communication system, which only uses the number of channels, the channel spacing, the total power of the modulated signal light, the gain coefficient, gain slope and noise figure of the optical amplifier , link loss, and the number of optical amplifiers, etc., can calculate the output OSNR, and can detect whether there is a fault in the link, and the complexity is low, the application is convenient, and it is suitable for high-speed and flexible optical fiber communication systems.

In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Embodiment one

Referring to Fig. 2, the present embodiment provides an OSNR calculation method for a cascaded optical amplifier communication system, the method includes the following steps:

Step S1, using the gain coefficients of optical amplifiers at various levels and the attenuation of optical fibers at each section, to calculate the net gain of optical amplifiers at all levels-fiber sections. In a specific implementation process, the optical amplifier is an erbium-doped fiber amplifier EDFA.

Step S2, using the number of channels, the channel spacing, the signal optical power modulated by the center frequency channel, the gain slopes of the optical amplifiers at all levels, and combining the net gains of the optical amplifiers at all levels-optical fiber sections obtained in S1, to calculate each channel and each level signal light power.

Step S3, according to the noise coefficient of optical amplifiers of each stage, combined with the signal optical power of each channel and each stage obtained in S2, the equivalent OSNR cost of the link is calculated.

Step S4. According to the determined OSNR of the input terminal, combined with the equivalent OSNR cost obtained in S3, the OSNR of the output terminal is calculated, that is, the target OSNR is finally obtained.

Embodiment two

This embodiment provides an OSNR calculation method for a cascaded optical amplifier communication system, the basic steps of which are the same as those in Embodiment 1, the difference being that in step S1 of the method, the gain coefficients, The fiber attenuation of each section is calculated by the following formula when calculating the net gain of the optical amplifier-fiber section at all levels:

Δ _j =G _j *L _j (1)

Among them, Δ _j represents the net gain of the j-th optical amplifier-fiber section, j∈[1,N], N is the total number of optical amplifier stages; G _j represents the gain coefficient of the j-th optical amplifier, and L _j represents the j-th Segment fiber attenuation.

Embodiment Three

An OSNR calculation method for a cascaded optical amplifier communication system provided in this embodiment has the same basic steps as in Embodiment 1, except that step S2 of the method specifically includes the following operations:

1) Determine the center frequency of the optical amplifier, and use the signal optical power modulated by the center frequency channel Combined with the net gain Δ _j of optical amplifiers at all levels calculated in S1, calculate the signal optical power of the center frequency channel in the optical amplifiers at all levels step by step Its calculation formula is:

Among them, i ₀ represents the center frequency channel number, and j represents the jth level optical amplifier;

2) Determine the number of channels Ch, and use the calculated center frequency channel signal optical power at all levels of optical amplifiers The channel spacing and the gain slopes of optical amplifiers at all levels are used to calculate the signal optical power Pin_e _{(i, j)} of each channel and each level. The calculation formula is:

Among them, i represents the i-th channel, i∈[1, Ch]; GT _j represents the gain slope of the j-level optical amplifier; B represents the channel spacing.

In the specific implementation process, after calculating the signal optical power Pin_e _{(i, j)} of each channel and level, the calculated Pin_e _{(i, j)} can be compared with the actual measured optical power Pin_e _{(i, j)} In contrast, if the difference between Pin_e _{(i, j)} and Pin_e _{(i, j)} exceeds the specified threshold (the specified threshold can be manually set through the upper management interface or software), it indicates that there is a fault in the link; if the two are basically the same , then the calculation of OSNR can be continued through step S3. It can be seen that, through the above operations, it is possible to detect whether there is a fault in the link, which can meet actual usage requirements.

Embodiment Four

An OSNR calculation method for a cascaded optical amplifier communication system provided in this embodiment has the same basic steps as in Embodiment 1, except that step S3 of the method specifically includes the following operations:

1) Calculate _{k (i, j) according to the noise coefficient of each level of optical amplifier combined with the signal optical power Pin_e (i, j) of} each channel and level obtained in S2, and this k _{(i, j)} reflects the jth level The influence of the noise characteristics of the optical amplifier on the i-th channel OSNR, its calculation formula is:

Among them, F _j represents the noise figure of the jth optical amplifier;

2) After accumulating the k _{(i, j)} of optical amplifiers at all levels, take the reciprocal, and calculate the impact OSNR _link of the entire link on OSNR, that is, the equivalent OSNR cost OSNR _link of the link. The calculation formula is:

Wherein, N1 represents the N1-level optical amplifier, and N2 represents the N2-level amplifier; when calculating the k _{(i, j)} of the cumulative optical amplifier from the 1st level to the j-th level, then N1=1, N2=j, and thus analogy.

Embodiment five

This embodiment provides an OSNR calculation method for a cascaded optical amplifier communication system, the basic steps of which are the same as those in Embodiment 1, the difference being that in step S4 of the method, according to the determined OSNR of the input terminal, combined with S3 The resulting equivalent OSNR cost, when calculating the output OSNR, is calculated using the following formula:

Among them, OSNR _in is the OSNR of the input terminal, OSNR _link is the equivalent OSNR cost obtained by S3, and OSNR _out is the OSNR of the output terminal.

Embodiment six

This embodiment provides an OSNR calculation method for a cascaded optical amplifier communication system, the basic steps of which are the same as those of Embodiment 1, except that this method also combines all the features of Embodiment 2 to Embodiment 5. Specifically, the method includes the following steps:

S1. Determine the gain coefficient G _j of the optical amplifiers at each level and the fiber attenuation L _j of each segment, and calculate the net gain Δ _j of the optical amplifier-fiber segment at each level according to formula (1).

S2. Determine the center frequency of the optical amplifier, and use the signal optical power modulated by the center frequency channel and the net gain Δ _j of the optical amplifier-fiber section at all levels calculated in S1, and calculate the signal optical power of the center frequency channel in the optical amplifiers at all levels according to the formula (2) step by step Determine the number of channels Ch, and use the calculated signal optical power of the center frequency channel in the optical amplifiers at all levels The channel spacing B and the gain slopes GT _j of the optical amplifiers at all levels are used to calculate the signal optical power Pin_e _{(i, j)} of each channel and each level according to the formula (3). At the same time, the calculated Pin_e _{(i, j)} can also be compared with the actually measured optical power Pin _{(i, j)} , so as to know whether there is a fault in the link.

S3, determine each level of optical amplifier noise factor F _j , in conjunction with the Pin _{(i, j)} obtained in S2, calculate k _{(i, j)} according to formula (4), it reflects the noise characteristics of the jth level EDFA to the ith channel Influence of OSNR; then according to the formula (5), the equivalent OSNR cost OSNR _link of the whole link is calculated after accumulating the k _{(i, j)} of optical amplifiers at all levels and taking the reciprocal.

S4. According to the determined OSNR of the input terminal, that is, OSNR _in (usually the default is infinite after the optical modulator), combined with the OSNR _link obtained in S3, calculate the OSNR of the output terminal according to formula (6), that is, OSNR _out , and obtain the final goal OSNR.

Embodiment seven

Based on the same inventive concept, as shown in FIG. 3 , an embodiment of the present invention also provides an OSNR calculation device for a cascaded optical amplifier communication system that implements the above method. The device includes a net gain calculation module, a signal optical power calculation module, an equivalent OSNR cost calculation module and a target OSNR calculation module; wherein:

The net gain calculation module is used to: use the gain coefficients of the optical amplifiers at all levels and the attenuation of each section of optical fiber to calculate the net gain of the optical amplifier-fiber section at all levels;

The signal optical power calculation module is used to: use the number of channels, the channel spacing, the signal optical power modulated by the center frequency channel, the gain slopes of the optical amplifiers at all levels, and combine the optical amplifiers at all levels-optical fiber sections obtained by the net gain calculation module The net gain of , calculate the signal optical power of each level of each channel;

The equivalent OSNR cost calculation module is used to: calculate the equivalent OSNR cost of the link according to the noise figure of each level of optical amplifier, combined with the signal optical power of each channel and each level obtained by the signal optical power calculation module;

The target OSNR calculation module is configured to: calculate the output terminal OSNR according to the determined input terminal OSNR combined with the equivalent OSNR cost obtained by the equivalent OSNR cost calculation module.

Embodiment eight

The basic structure of the OSNR calculation device used in the cascaded optical amplifier communication system provided by this embodiment is the same as that of the seventh embodiment, except that, as shown in FIG. 4 , the device also includes a fault detection module. The fault detection module is used to: compare the signal optical power of each channel and level calculated by the signal optical power calculation module with the actual measured optical power, and if the difference between the two exceeds the specified threshold, it is determined that there is a fault in the link. Fault.

Based on EDFA link analysis, the present invention calculates OSNR through the noise characteristics of the optical amplifier and the amplified operating conditions, and has no requirements on other devices and structures at the transceiver end. Compared with the existing technology, the measurement range can reach more than 20dB, the accuracy can reach within 1dB, the system stability is good, the calculation complexity is low, and it has certain significance for the design of future optical transmission systems.

In order to further verify the technical effect that the present invention can achieve, the technical effect of the OSNR calculation scheme for the cascaded optical amplifier communication system proposed according to the present invention will be described in detail below in conjunction with the accompanying drawings and simulation examples.

In this simulation example, the specific process of this method and the final optical signal-to-noise ratio calculation effect are illustrated by performing OSNR calculation on a DWDM optical fiber communication system with a transmission rate of 8 spans, each span length is 100km, and the rate is 9*10Gbps.

The entire coherent optical transmission system is built in VPI (optical fiber system simulation software launched by VPIphotonics). The power of the optical signal after modulation is -18dBm. The gain of each optical amplifier and the loss of the optical fiber link are shown in Figure 5. Optical amplifier, the noise figure is 6dB, the first two digits of the lower four digits represent the gain factor, from the first to the tenth level are 18dB, 25dB, 25dB, 25dB, 14dB, 18dB, 25dB, 25dB, 25dB, 25dB; The value below the link is the loss value of the optical fiber link, which is 25dB in the simulation, and the loss of ROAD M (Reconfigurable Optical Add-Drop Multiplexer, reconfigurable optical add-drop multiplexer) is 7dB. The typical value of the gain slope is -1dB/THz, but the pre-emphasis on the two 1821 optical amplifiers is 3dB, that is, the single-wave power of 1529.16nm is 3dB higher than that of 1560.20nm, and the power from short-wave to long-wave decreases by 3/79dB.

The specific processing method is as follows:

1. According to the content in step S1, it is easy to obtain the net gain Δ _j of each stage through the formula (1). In this system, Δ ₁ = Δ ₆ = -7dB, Δ ₂ = Δ ₃ = Δ ₄ = Δ ₇ = Δ ₈ =Δ ₉ =0, Δ ₅ =7dB.

2. According to the content in step S2, use the net gain to calculate the signal optical power of the center frequency channel at all levels of optical amplifiers, and then use the gain slope value and pre-emphasized parameters to calculate the signal optical power Pin_e _{(i, j)} . In the simulation, since there is no link fault, Pin_e _{(i, j)} is the same as Pin _{(i, j)} , as shown in Figure 6. Among them, f represents the channel frequency, the unit is THz; Pin represents the power entering the EDFA, the unit is dBm.

3. According to the content in step S3, first calculate the OSNR cost of each EDFA, that is, the influence of the noise characteristics of each EDFA on the i-th channel OSNR, as shown in FIG. 7 . Wherein, k reflects the OSNR cost of each EDFA, OSNR _EDFAi =1/k _i . Accumulate them to get the link OSNR cost, namely

4. According to the content in step S4, add the reciprocals of OSNR _in and OSNR _link respectively to obtain the reciprocal of OSNR _out , thereby obtaining the target output terminal OSNR, as shown in FIG. 8 . Among them, the unit of OSNR is dB. In order to test its accuracy, the calculation results of this method are compared with the simulation measurement results, and the difference ΔOSNR is shown in Figure 8. ΔOSNR is in dB.

For a system with 9 channels and 10 optical amplifiers, the above-mentioned process is used to calculate one by one to obtain the OSNR of each channel at the output end. The simulation results show that the OSNR calculated by this method is within 1dB of the OSNR measured by simulation. Therefore, the calculation error of the optical signal-to-noise ratio obtained by this method is small, and can meet the requirements of actual use.

The present invention is not limited to the above-mentioned embodiments. For those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also considered protection of the present invention. within range. The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims (10)

1. a kind of OSNR computational methods for cascading image intensifer communication system, which is characterized in that this method includes following step Suddenly：

S1, the gain coefficient using image intensifers at different levels, each section of optical fiber attenuation, calculate having a net increase of for image intensifer-fiber segment at different levels Benefit；

S2, the increasing of signal light power, image intensifer at different levels after channel number, channel spacing, centre frequency Channel Modulation is utilized Beneficial slope, and the net gain of image intensifer-fiber segments at different levels obtained by S1 is combined, calculate the signal light work(of each every grade of channel Rate；

S3, according to every grade of noise of optical amplifier coefficient, the signal light power of each every grade of channel in conjunction with obtained by S2, calculate link Equivalent OSNR costs；

S4, according to determining input terminal OSNR, the equivalent OSNR costs in conjunction with obtained by S3 calculate output end OSNR.

2. the OSNR computational methods as described in claim 1 for cascading image intensifer communication system, which is characterized in that in step Further include following operation after rapid S2：By the signal light power for each every grade of the channel being calculated and actually measured light work( Rate compares, if the two gap is more than specified threshold, judges to break down in link.

3. the OSNR computational methods as described in claim 1 for cascading image intensifer communication system, it is characterised in that：Step In S1, using the gain coefficient of image intensifers at different levels, each section of optical fiber attenuation, the net gain of image intensifer-fiber segments at different levels is calculated When, it is calculated using following formula：

Δ_j=G_j*L_j

Wherein, Δ_jIndicate the net gain of j-th stage image intensifer-fiber segment, j ∈ [1, N]；N indicates the total series of image intensifer, is big In 1 positive integer；G_jIndicate the gain coefficient of j-th stage image intensifer, L_jIndicate jth section optical fiber attenuation.

4. the OSNR computational methods as claimed in claim 3 for cascading image intensifer communication system, which is characterized in that step S2 specifically includes following operation：

1) centre frequency for determining image intensifer utilizes the signal light power after the centre frequency Channel ModulationAnd it ties Close the net gain Δ of calculated image intensifer-fiber segments at different levels in S1_j, centre frequency channel is calculated step by step in light amplification at different levels The signal light power of deviceIts calculation formula is：

Wherein, i₀Indicate that centre frequency channel number, j indicate j-th stage image intensifer；

2) determine channel number Ch, using calculated centre frequency channel image intensifers at different levels signal light powerThe gain slope of channel spacing and image intensifer at different levels calculates the signal light power of each every grade of channel Pin_e_{(i, j)}, calculation formula is：

Wherein, i indicates the i-th channel, i ∈ [1, Ch]；GT_jIndicate the gain slope of j-th stage image intensifer；B indicates channel spacing.

5. the OSNR computational methods as claimed in claim 4 for cascading image intensifer communication system, which is characterized in that step S3 specifically includes following operation：

1) according to every grade of noise of optical amplifier coefficient, the signal light power Pin_e of each every grade of channel in conjunction with obtained by S2_{(i, j)}Meter Calculate k_{(i, j)}, the k_{(i, j)}For the influence of the i-th channel of noise characteristic pair OSNR of j-th stage image intensifer, calculation formula is：

Wherein, F_jIndicate j-th stage noise of optical amplifier coefficient；

2) k of image intensifers at different levels is accumulated_{(i, j)}It is inverted afterwards, calculate the equivalent OSNR costs OSNR of entire link_link, meter Calculating formula is：

Wherein, N1 indicates that N1 grades of image intensifers, N2 indicate N2 grades of amplifiers；When calculating is from the 1st grade to the accumulation light of j-th stage The k of amplifier_{(i, j)}, then N1=1, N2=j, and so on.

6. the OSNR computational methods as claimed in claim 5 for cascading image intensifer communication system, it is characterised in that：Step In S4, according to determining input terminal OSNR, the equivalent OSNR costs in conjunction with obtained by S3, when calculating output end OSNR, use is following Formula calculates：

Wherein, OSNR_inFor input terminal OSNR, OSNR_linkFor the equivalent OSNR costs obtained by S3, OSNR_outFor output end OSNR.

7. special such as the OSNR computational methods according to any one of claims 1 to 6 for cascading image intensifer communication system Sign is：The image intensifer is EDFA Erbium-Doped Fiber Amplifier EDFA.

8. special such as the OSNR computational methods according to any one of claims 1 to 6 for cascading image intensifer communication system Sign is：The cascade image intensifer communication system includes laser light source, optical modulator and N number of cascade image intensifer；

The optical modulator is connected to the output end of laser light source, the optical signal sent out for modulating laser light source；N number of grade It is connected between the image intensifer of connection by being used for transmission the optical fiber of optical signal, and first order image intensifer is connected to optical modulator Output end, the modulated optical signal for exporting optical modulator export after being amplified, and N grades of image intensifers are connected to optical fiber Output end, for will be exported after the optical signal amplification after transmission.

9. a kind of OSNR computing devices for cascading image intensifer communication system for realizing claim 1 the method, special Sign is：The device includes net gain computing module, signal light power computing module, equivalent OSNR costs computing module and target OSNR computing modules；

The net gain computing module is used for：Using the gain coefficient of image intensifers at different levels, each section of optical fiber attenuation, light at different levels are calculated The net gain of amplifier-fiber segment；

The signal light power computing module is used for：Utilize the signal after channel number, channel spacing, centre frequency Channel Modulation The gain slope of luminous power, image intensifer at different levels, and image intensifer-optical fiber at different levels in conjunction with obtained by the net gain computing module The net gain of section, calculates the signal light power of each every grade of channel；

The equivalent OSNR costs computing module is used for：According to every grade of noise of optical amplifier coefficient, in conjunction with the signal light power The signal light power of each every grade of channel obtained by computing module calculates the equivalent OSNR costs of link；

The target OSNR computing modules are used for：According to determining input terminal OSNR, mould is calculated in conjunction with the equivalent OSNR costs Equivalent OSNR costs obtained by block calculate output end OSNR.

10. the OSNR computing devices as claimed in claim 9 for cascading image intensifer communication system, it is characterised in that：It should Device further includes fault detection module, which is used for：The signal light power computing module is calculated The signal light power of each every grade of channel is compared with actually measured luminous power, if the two gap is more than specified threshold, is judged It breaks down in link.