CN104363048A - Coherent mixing based in-band optical signal to noise ratio monitoring method and calculation system - Google Patents

Abstract

The present invention relates to the communication field, and discloses an in-band optical signal-to-noise ratio monitoring method and an optical signal-to-noise ratio calculation system based on coherent frequency mixing. The method is applied to the optical signal-to-noise ratio calculation system, and the system includes: a polarization controller, The input end of the polarization controller is connected to the signal light; the intrinsic laser; the coupler; the balance detector; the electric power meter; the optical signal-to-noise ratio calculator; The wavelength of the intrinsic light is the same; the first power value and the second power value are obtained through the detection of the electric power meter, and the first power value and the second power value are sent to the optical signal-to-noise ratio calculator, wherein the first power value is The power value detected by the electric power meter when the polarization state of the signal light and the intrinsic light is the same, and the second power value is the power value detected by the electric power meter when the polarization state of the signal light and the intrinsic light is perpendicular; optical signal-to-noise ratio calculator The optical signal-to-noise ratio in the channel to be tested is obtained by calculating the first power value and the second power value.

Description

A method and calculation system for in-band optical signal-to-noise ratio monitoring based on coherent frequency mixing

technical field

The invention relates to the communication field, in particular to an in-band optical signal-to-noise ratio monitoring method and calculation system based on coherent frequency mixing.

Background technique

As people's requirements for bandwidth are getting higher and higher, the single-channel rate of the optical communication backbone network is evolving from 40Gb/s to 100Gb/s and above, and the wavelength interval of the wavelength division multiplexing (WDM: Wavelength Division Multiplexing) system is also from 50GHz to 50GHz. 25GHz and even 12.5GHz evolution. When the wavelength interval is very small, the traditional linear interpolation method has been unable to measure the noise power between channels, and it is also unable to fit the noise power within the band. And with the introduction of optical add-drop multiplexer (ROADM: optical add-drop multiplexer), the signals of different channels will pass through different links, which is equivalent to passing through different filtering effects, which leads to spontaneous emission of large radiation noise in the band ( ASE: amplified spontaneous emission) is constantly accumulating, and the out-of-band ASE is at a lower level due to the filter limit, so the in-band and out-of-band ASE noises are not the same, and the measured optical signal-to-noise ratio of the in-band noise is fitted by the out-of-band noise (OSNR: Optical Signal NoiseRatio) method is not accurate. In addition, with the use of reconfigurable optical add-drop multiplexers, a large number of optical filters are added, and the noise outside the signal is suppressed by filtering, which is smaller than the in-band noise existing at the wavelength position of the actual signal, resulting in the use of inter-channel noise The method of calculating the in-band noise of a signal is no longer accurate. And as the signal rate increases, the spectral width of the signal will also increase. When the spectral width is close to the channel spacing, a part of the signal will be regarded as noise when fitting the out-of-band noise, resulting in a large error.

If the traditional polarization multiplexing and zeroing method is used to calculate the in-band OSNR, it mainly needs to use a polarization beam splitter, a polarization controller and a balance detector. By adjusting the polarization controller, the two outputs of the polarization beam splitter The output optical power at the end is the same, and then the OSNR is calculated after being converted into an electrical signal by a balanced detector. Due to the need to additionally use a polarization beam splitter and a high-speed detector, it has a technical problem of high cost.

Contents of the invention

The invention provides an in-band optical signal-to-noise ratio monitoring method and calculation system based on coherent frequency mixing to solve the technical problems in the prior art that the measurement of OSNR for high-speed signals is either not accurate enough or has high cost.

In the first aspect, an embodiment of the present invention provides an in-band OSNR monitoring method based on coherent frequency mixing, wherein the method is applied to an OSNR calculation system, and the system includes: a polarization controller , the input end of the polarization controller is connected to the signal light; the intrinsic laser; the coupler, the first input end of the coupler is connected to the output end of the polarization controller, and the second input end of the coupler Connected to the output end of the intrinsic laser; a balanced detector, connected to the coupler; an electric power meter, connected to the balanced detector; an optical signal-to-noise ratio calculator, connected to the electric power meter; the method include:

The wavelength of the signal light controlling the channel to be tested is the same as the wavelength of the intrinsic light generated by the intrinsic laser;

The first power value and the second power value are obtained through the detection of the electric power meter, and the first power value and the second power value are sent to the optical signal-to-noise ratio calculator, wherein the first power The value is the power value detected by the electric power meter when the polarization state of the signal light is the same as that of the intrinsic light, and the second power value is when the polarization state of the signal light is perpendicular to the intrinsic light, The power value detected by the electric power meter;

The optical signal-to-noise ratio calculator calculates and obtains the optical signal-to-noise ratio in the channel to be tested by using the first power value and the second power value.

Optionally, the optical signal-to-noise ratio calculator calculates and obtains the optical signal-to-noise ratio by the following formula:

$\mathrm{<span\; class="notranslate">\; OSNR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}{<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}$

Among them, OSNR represents the optical signal-to-noise ratio;

Ps represents signal power;

P _n represents the noise power;

B _r represents the effective bandwidth of the channel to be tested;

B _n is the noise equivalent bandwidth;

<I _max (t)> represents the first power value;

<I _min (t)> represents the second power value.

Optionally, the obtaining the first power value and the second power value through the detection of the electric power meter specifically includes:

controlling the polarization state of the signal light to be the same as that of the intrinsic light, and obtaining the first power value through detection by the electric power meter;

The signal light is controlled to be perpendicular to the polarization state of the intrinsic light, and is detected by the electric power meter to obtain a second power value.

Optionally, the obtaining the first power value by detecting the electric power meter and obtaining the second power value by detecting the electric power meter specifically include:

Adjusting the polarization state of the polarization controller N times, and then obtaining N power values through the detection of the electric power meter, where N is a positive integer greater than or equal to 2;

determining the first power value with the highest power value from the N power values;

The lowest power value is determined from the N power values to be the second power value.

Optionally, before the wavelength of the signal light controlling the channel to be tested is the same as the wavelength of the intrinsic light generated by the intrinsic laser, the method further includes:

The channel to be tested is selected from multiple channels, and the signal light is the signal light transmitted by the channel to be tested.

In a second aspect, an embodiment of the present invention provides an optical signal-to-noise ratio calculation system, including:

a polarization controller, the input end of the polarization controller is connected to signal light, and the polarization controller is used to change the polarization state of the signal light;

an intrinsic laser for generating intrinsic light;

A coupler, the first input end of the coupler is connected to the output end of the polarization controller, the second input end of the coupler is connected to the output end of the intrinsic laser, and the coupler is used for the mixing the signal light and the intrinsic light;

A balanced detector connected to the coupler, the balanced detector is used to convert the optical signal input into the balanced detector into an electrical signal, and remove the DC signal in the electrical signal;

An electric power meter, connected to the balance detector, is used to detect and obtain a first power value and a second power value, wherein the first power value is obtained when the polarization state of the signal light is the same as that of the intrinsic light The power value detected by the electric power meter, the second power value is the power value detected by the electric power meter when the polarization state of the signal light is perpendicular to the intrinsic light;

an optical signal-to-noise ratio calculator, connected to the electric power meter, for obtaining the first power value and the second power value from the electric power meter, and using the first power value and the second power The value is calculated to obtain the optical signal-to-noise ratio in the channel to be tested.

Optionally, the optical signal-to-noise ratio calculator is specifically used to calculate and obtain the optical signal-to-noise ratio by the following formula:

$\mathrm{<span\; class="notranslate">\; OSNR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}{<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}$

Among them, OSNR represents the optical signal-to-noise ratio;

Ps represents signal power;

P _n represents the noise power;

B _r represents the effective bandwidth of the channel to be tested;

B _n is the noise equivalent bandwidth;

<I _max (t)> represents the first power value;

<I _min (t)> represents the second power value.

Optionally, the electric power meter is specifically used for:

When the polarization state of the signal light is the same as that of the intrinsic light, detecting and obtaining the first power value;

When the signal light is perpendicular to the polarization state of the intrinsic light, the second power value is obtained through detection.

Optionally, the electric power meter is specifically used for:

Through N adjustments of the polarization state of the polarization controller, N power values are obtained through detection, and N is a positive integer greater than or equal to 2;

determining the first power value with the highest power value from the N power values;

The lowest power value is determined from the N power values to be the second power value.

Optionally, the system also includes:

An adjustment filter is used to select the channel to be tested from multiple channels, and the signal light is the signal light transmitted by the channel to be tested.

The beneficial effects of the present invention are as follows:

Since in the embodiment of the present invention, an in-band OSNR monitoring method based on coherent frequency mixing is provided, the method is applied to an OSNR calculation system, and the system includes: a polarization controller, an input terminal of the polarization controller Access signal light; intrinsic laser; coupler, the first input end of the coupler is connected to the output end of the polarization controller, and the second input end of the coupler is connected to the output end of the intrinsic laser; the balance detector is connected to A coupler; an electric power meter, connected to the balance detector; an optical signal-to-noise ratio calculator, connected to the electric power meter; the method includes: controlling the wavelength of the signal light of the channel to be measured to be the same as the wavelength of the intrinsic light generated by the intrinsic laser; Obtain the first power value and the second power value through the detection of the electric power meter, and send the first power value and the second power value to the optical signal-to-noise ratio calculator, wherein the first power value is the polarization of the signal light and the intrinsic light The power value detected by the electric power meter when the state is the same, the second power value is the power value detected by the electric power meter when the polarization state of the signal light is perpendicular to the intrinsic light; the optical signal-to-noise ratio calculator uses the first power value and the second The power value is calculated to obtain the optical signal-to-noise ratio in the channel to be tested. That is to say, in the above scheme, by changing the polarization state of the signal light, when mixing with the intrinsic light, the different polarization characteristics of the signal and noise are used, and the OSNR is measured by balancing the different output responses of the detector after mixing. The noise at the in-band center wavelength is directly measured, so there will be no error in fitting the in-band noise through the out-of-band noise, thereby improving the accuracy of detecting the in-band OSNR; and will not be affected by the optical filter Influence, and then further improve the accuracy;

And compared with the traditional polarization multiplexing and zeroing method, this method can be perfectly combined with the current coherent detection system, and does not require an additional polarization beam splitter, thereby having the technical effect of reducing costs.

Description of drawings

1 is a structural diagram of an optical signal-to-noise ratio calculation system in an embodiment of the present invention;

2 is a flow chart of an in-band OSNR monitoring method based on coherent frequency mixing in an embodiment of the present invention;

Fig. 3 is a flow chart of the first way of determining the first power value and the second power value in the in-band optical signal-to-noise ratio monitoring method based on coherent frequency mixing in the embodiment of the present invention;

Fig. 4 is a flow chart of the second way of determining the first power value and the second power value in the in-band OSNR monitoring method based on coherent frequency mixing according to the embodiment of the present invention;

FIG. 5 is a structural diagram of a CO-OFDM system in Embodiment 1 of the present invention;

6 is a comparison diagram between the calculated value and the standard value of OSNR determined based on the CO-OFDM system introduced in Embodiment 1 in Embodiment 2 of the present invention;

FIG. 7 is a schematic diagram of errors of calculated values of OSNR determined based on the CO-OFDM system introduced in Embodiment 1 in Embodiment 2 of the present invention.

Detailed ways

The present invention provides an in-band optical signal-to-noise ratio monitoring method and calculation system based on coherent frequency mixing to solve the technical problem in the prior art that the actual operation is difficult or the cost is high when measuring OSNR for high-speed signals.

The general idea of the embodiment of the present invention is as follows:

Since in the embodiment of the present invention, an in-band OSNR monitoring method based on coherent frequency mixing is provided, the method is applied to an OSNR calculation system, and the system includes: a polarization controller, an input terminal of the polarization controller Access signal light; intrinsic laser; coupler, the first input end of the coupler is connected to the output end of the polarization controller, and the second input end of the coupler is connected to the output end of the intrinsic laser; the balance detector is connected to A coupler; an electric power meter, connected to the balance detector; an optical signal-to-noise ratio calculator, connected to the electric power meter; the method includes: controlling the wavelength of the signal light of the channel to be measured to be the same as the wavelength of the intrinsic light generated by the intrinsic laser; Obtain the first power value and the second power value through the detection of the electric power meter, and send the first power value and the second power value to the optical signal-to-noise ratio calculator, wherein the first power value is the polarization of the signal light and the intrinsic light The power value detected by the electric power meter when the state is the same, the second power value is the power value detected by the electric power meter when the polarization state of the signal light is perpendicular to the intrinsic light; the optical signal-to-noise ratio calculator uses the first power value and the second The power value is calculated to obtain the optical signal-to-noise ratio in the channel to be tested. That is to say, in the above scheme, by changing the polarization state of the signal light, when mixing with the intrinsic light, the different polarization characteristics of the signal and noise are used, and the OSNR is measured by balancing the different output responses of the detector after mixing. The noise at the in-band center wavelength is directly measured, so there will be no error in fitting the in-band noise through the out-of-band noise, which can improve the accuracy of detecting the in-band OSNR; and will not be affected by the optical filter Influence, and then further improve the accuracy;

And compared with the traditional polarization multiplexing and zeroing method, this method can be perfectly combined with the current coherent detection system, and does not require an additional polarization beam splitter, thereby having the technical effect of reducing costs.

In order to better understand the above technical solutions, the technical solutions of the present invention will be described in detail below through the accompanying drawings and specific examples. It should be understood that the embodiments of the present invention and the specific features in the examples are detailed descriptions of the technical solutions of the present invention, and It is not a limitation to the technical solutions of the present invention, and the embodiments of the present invention and the technical features in the embodiments can be combined with each other under the condition of no conflict.

In the first aspect, an embodiment of the present invention provides an in-band OSNR monitoring method based on coherent frequency mixing, which is applied to an OSNR calculation system, such as: coherent optical OFDM System (CO-OFDM: Coherent Optical Orthogonal Frequency Division Multiplexing), WDM system, etc., please refer to Figure 1, the system includes:

A polarization controller 10, the input end of the polarization controller is connected to the signal light for changing the polarization state of the signal light;

Intrinsic laser 11, the intrinsic laser 11 is used to generate intrinsic light;

A coupler 12, the first input end of the coupler 12 is connected to the output end of the polarization controller 10, the second input end of the coupler 12 is connected to the output end of the intrinsic laser 11, and the coupler 12 is used for the signal light and the intrinsic laser The light is mixed, and the coupler 12 is, for example, a 50:50 2×2 coupler;

A balanced detector 13, connected to the coupler 12, the balanced detector 13 is used to convert the optical signal input into the balanced detector 13 into an electrical signal, and remove the DC signal in the electrical signal;

Power meter 14, connected to balance detector 13;

The optical signal-to-noise ratio calculator 15 is connected to the electric power meter 14;

Referring to Figure 2, the method includes the following steps:

Step S201: controlling the wavelength of the signal light of the channel to be tested to be the same as the wavelength of the intrinsic light generated by the intrinsic laser 11;

Step S202: Obtain the first power value and the second power value through the detection of the electric power meter 14, and send the first power value and the second power value to the optical signal-to-noise ratio calculator 15, wherein the first power value is the signal light and When the polarization state of the intrinsic light is the same as the power value detected by the electric power meter 14, the second power value is the power value detected by the electric power meter 14 when the polarization state of the signal light is perpendicular to the intrinsic light;

Step S203: The OSNR calculator 15 calculates and obtains the OSNR in the channel to be tested by using the first power value and the second power value.

In a specific implementation process, the frequency of the intrinsic light generated by the intrinsic laser 11 can be controlled, so that the wavelength of the intrinsic light and the signal light can be controlled to be the same.

In the specific implementation process, in step S202, the electric power meter 14 can obtain the first power value and the second power value in various ways. situation.

The first one is to obtain the first power value and the second power value through the detection of the electric power meter 14, please refer to FIG. 3, which specifically includes:

Step S301: The polarization state of the control signal light is the same as that of the intrinsic light, and the first power value is obtained through detection by the electric power meter 14;

Step S302: Control the signal light to be perpendicular to the polarization state of the intrinsic light, and use the electric power meter 14 to detect and obtain a second power value.

In the specific implementation process, the polarization state of the intrinsic light of the intrinsic laser 11 is determined, so in step S301, after the polarization controller 10 receives the signal light, the polarization state of the signal light can be detected first, and then the signal light The polarization state of the signal light is compared with the polarization state of the intrinsic light, and then the control parameters of the polarization controller 10 are determined, so that after the signal light passes through the polarization controller 10, the polarization state of the signal light is the same as that of the intrinsic light.

Usually, the calculated first power value includes the power of the signal and half of the noise within the bandwidth, as follows:

$<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; LO</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\sqrt{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; LO</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ]</span>$

Wherein, I _max (t) represents the first power value;

R represents the responsivity of the balance detector 13;

Ps represents signal power;

P _LO represents the intrinsic optical power;

_Pn represents the noise power.

In step S302, after the polarization controller 10 receives the signal light, the polarization state of the signal light can also be detected first, and then the polarization state of the signal light determines the control parameters of the polarization controller 10, so that the signal light passes through the polarization controller 10 Afterwards, the polarization state of the signal light is perpendicular to that of the intrinsic light.

Normally, the obtained second power value contains the power of half the noise within the bandwidth of the balance detector 13, specifically as follows:

$<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}\sqrt{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; LO</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ]</span>$

In the above solution, the electric power meter 14 only needs to detect twice to accurately determine the first power value and the second power value, thereby reducing the number of detections of the electric power meter 14, thereby reducing the processing load of the system.

The second type is to obtain the first power value through the detection of the electric power meter 14 and obtain the second power value through the detection of the electric power meter 14, please refer to FIG. 4 , which specifically includes:

Step S401: Adjust the polarization state of the polarization controller 10 N times, and then obtain N power values through the detection of the electric power meter 14, where N is a positive integer greater than or equal to 2;

Step S402: Determine the highest power value from the N power values as the first power value;

Step S403: Determine the lowest power value from the N power values to be the second power value.

In step S401, N may be 2, 4, 10, etc., wherein the higher the value of N, the more accurate the determined first power value will be.

In step S402 and step S403, a comparator may be set, and then the highest power value determined by the comparator is the first power value, and the lowest power value determined by the comparator is the second power value.

In the above solution, after the signal light enters the polarization controller 10, the first power value and the second power value can be determined without detecting the polarization state of the signal light, thus reducing the implementation complexity.

In the specific implementation process, in step S203, the optical signal-to-noise ratio calculator 15 calculates and obtains the optical signal-to-noise ratio by the following formula:

$\mathrm{<span\; class="notranslate">\; OSNR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}{<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; ]</span>$

Among them, OSNR represents the optical signal-to-noise ratio;

Ps represents signal power;

P _n represents the noise power;

B _r represents the effective bandwidth of the channel to be tested;

B _n is the noise equivalent bandwidth;

<I _max (t)> represents the first power value;

<I _min (t)> represents the second power value.

As a further preferred embodiment, before controlling the wavelength of the signal light of the channel to be tested to be the same as the wavelength of the intrinsic light generated by the intrinsic laser 11, the method also includes:

The channel to be tested is selected from the multiple channels, and the signal light is the signal light transmitted by the channel to be tested.

In the specific implementation process, some systems only include one channel (for example: CO-OFDM system), in this case, it is enough to receive the signal light directly through this channel; some systems can include multiple channels (for example: WDM), in this case, it is first necessary to select the channel to be tested from multiple channels, and then obtain signal light from the channel to be tested, for example: to select the channel to be tested from multiple channels by adjusting the filter.

Furthermore, since the spectrum of the CO-OFDM signal is flat, low-speed detectors can be used to detect the signal power at low frequencies, and then the signal power in the entire spectrum can be calculated by using the flat spectrum of the signal. Therefore, for the CO-OFDM system Spectrum characteristics only need to use low-speed balanced detectors, which can further reduce costs. Moreover, since the dispersion and polarization mode dispersion have a greater impact on the RF power at high frequencies, and have little impact on the RF power at low frequencies, this scheme has a strong impact on both dispersion and polarization mode dispersion in the CO-OFDM system. The resistance effect of the traditional polarization nulling method is greatly affected by the polarization mode dispersion.

Further, the CO-OFDM system can be perfectly nested in the WDM system. The advantage of this solution for the CO-OFDM system is that the low-speed balance detector 13 can also be used, which greatly reduces the cost.

In the second aspect, based on the same inventive concept, an embodiment of the present invention introduces an optical signal-to-noise ratio calculation system, please continue to refer to Figure 1, including:

A polarization controller 10, the input end of the polarization controller 10 is connected to the signal light, and the polarization controller 10 is used to change the polarization state of the signal light;

Intrinsic laser 11, the intrinsic laser 11 is used to generate intrinsic light;

A coupler 12, the first input end of the coupler 12 is connected to the output end of the polarization controller 10, the second input end of the coupler 12 is connected to the output end of the intrinsic laser 11, and the coupler 12 is used for the signal light and the intrinsic laser Light mixing;

A balanced detector 13, connected to the coupler 12, the balanced detector 13 is used to convert the optical signal input into the balanced detector 13 into an electrical signal, and remove the DC signal in the electrical signal;

The electric power meter 14 is connected to the balance detector 13, and is used to detect and obtain the first power value and the second power value, wherein the first power value is the power detected by the electric power meter 14 when the polarization state of the signal light and the intrinsic light are the same value, the second power value is the power value detected by the electric power meter 14 when the polarization state of the signal light is perpendicular to the intrinsic light;

The optical signal-to-noise ratio calculator 15 is connected to the electric power meter 14, and is used to obtain the first power value and the second power value from the electric power meter 14, and obtain the optical signal in the channel to be tested by calculating the first power value and the second power value. SNR.

Optionally, the optical signal-to-noise ratio calculator 15 is specifically configured to calculate and obtain the optical signal-to-noise ratio by the following formula:

$\mathrm{<span\; class="notranslate">\; OSNR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}{<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ></span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; ]</span>$

Among them, OSNR represents the optical signal-to-noise ratio;

Ps represents signal power;

P _n represents the noise power;

B _r represents the effective bandwidth of the channel to be tested;

B _n is the noise equivalent bandwidth;

<I _max (t)> represents the first power value;

<I _min (t)> represents the second power value.

Optionally, the electric power meter 14 is specifically used for:

When the polarization state of the signal light is the same as that of the intrinsic light, the detection obtains the first power value;

When the polarization state of the signal light is perpendicular to the intrinsic light, the detection obtains the second power value.

Optionally, the electric power meter 14 is specifically used for:

Through N adjustments of the polarization state of the polarization controller 10, N power values are obtained through detection, and N is a positive integer greater than or equal to 2;

Determining the highest power value from the N power values as the first power value;

The lowest power value is determined from the N power values as the second power value.

Optionally, please continue to refer to Figure 1, the system also includes:

The adjustment filter 16 is used to select the channel to be tested from multiple channels, and the signal light is the signal light transmitted by the channel to be tested.

In order to enable those skilled in the art to further understand the coherent mixing-based in-band OSNR monitoring method introduced in the embodiments of the present invention, it will be introduced based on specific applications below.

Embodiment one

In this embodiment, the CO-OFDM system will be introduced as an example of the optical signal-to-noise ratio calculation system. Please refer to FIG. 5. The CO-OFDM system includes the following structure:

An external cavity laser 50, used to generate an optical signal;

The IQ modulator 51 is connected to the external cavity laser 50 and is used to modulate the electrical signal into the optical domain;

ASE (amplified spontaneous emission: amplifier spontaneous emission) noise source 52, for generating ASE noise;

An attenuator 53, connected to the ASE noise source 52, for adjusting the size of the ASE noise;

50:50 coupler 54, connected to IQ modulator 51 and attenuator 53;

The 10:90 coupler 55 is connected to the 50:50 coupler 54, wherein the 50:50 coupler 54 and the 10:90 coupler 55 are used to couple the ASE noise with the optical signal, so that the OSNR can be changed;

The tunable bandpass filter 56 is connected to the 10:90 coupler 55 and is used to select the wavelength to be monitored in a multi-wavelength system (for example: WDM system). If the system is a single wavelength system, the tunable bandpass filter is not required filter 56;

Spectrometer 57, used to measure the standard value of OSNR;

A polarization controller 58, connected to the tunable bandpass filter 56, is used to control the polarization state of the optical signal;

Intrinsic laser 59, used to generate intrinsic light;

2X2 50:50 coupler 60, connected to polarization controller 58 and intrinsic laser 59, for mixing intrinsic light and optical signal;

Balanced detector 61, connected to 2X2 50:50 coupler 60, used to convert the optical signal input into the balanced detector into an electrical signal, and remove the DC signal in the electrical signal;

The electric power meter 62 is used to detect and obtain the first power value and the second power value, wherein the first power value is the power value detected by the electric power meter when the polarization state of the signal light and the intrinsic light are the same, and the second power value is When the signal light is perpendicular to the polarization state of the intrinsic light, the power value detected by the electric power meter.

Embodiment two

In this embodiment, the calculation results for the CO-OFDM system will be introduced. What the system transmits is a 16QAM signal of 40Gb/s. The obtained OSNR monitoring results are shown in Figure 6, where the vertical axis of Figure 6 represents the formula [3] The calculated value of the determined OSNR, the horizontal axis of Figure 6 represents the standard value of the OSNR measured by the spectrometer 57, as can be seen from Figure 6, the calculated value of the OSNR is not much different from the standard value, thus showing that the accuracy is relatively high.

In addition, please refer to Figure 7. The ordinate of Figure 7 indicates the error of the calculated value of OSNR relative to the standard value, and the abscissa indicates the standard value of OSNR. It can be seen from Figure 7 that when OSNR changes within the range of 10-25dB, The error of the calculated value is within 0.5dB.

One or more embodiments of the present invention have at least the following beneficial effects:

Since in the embodiment of the present invention, an in-band OSNR monitoring method based on coherent frequency mixing is provided, the method is applied to an OSNR calculation system, and the system includes: a polarization controller, an input terminal of the polarization controller Access signal light; intrinsic laser; coupler, the first input end of the coupler is connected to the output end of the polarization controller, and the second input end of the coupler is connected to the output end of the intrinsic laser; the balance detector is connected to A coupler; an electric power meter, connected to the balance detector; an optical signal-to-noise ratio calculator, connected to the electric power meter; the method includes: controlling the wavelength of the signal light of the channel to be measured to be the same as the wavelength of the intrinsic light generated by the intrinsic laser; Obtain the first power value and the second power value through the detection of the electric power meter, and send the first power value and the second power value to the optical signal-to-noise ratio calculator, wherein the first power value is the polarization of the signal light and the intrinsic light The power value detected by the electric power meter when the state is the same, the second power value is the power value detected by the electric power meter when the polarization state of the signal light is perpendicular to the intrinsic light; the optical signal-to-noise ratio calculator uses the first power value and the second The power value is calculated to obtain the optical signal-to-noise ratio in the channel to be tested. That is to say, in the above scheme, by changing the polarization state of the signal light, when mixing with the intrinsic light, the different polarization characteristics of the signal and noise are used, and the OSNR is measured by balancing the different output responses of the detector after mixing. The noise at the in-band center wavelength is directly measured, so there will be no error in fitting the in-band noise through the out-of-band noise, thereby improving the accuracy of detecting the in-band OSNR; and will not be affected by the optical filter Influence, and then further improve the accuracy;

And compared with the traditional polarization multiplexing and zeroing method, this method can be perfectly combined with the current coherent detection system, and does not require an additional polarization beam splitter, thereby having the technical effect of reducing costs.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies thereof, the present invention also intends to include these modifications and variations.

Claims (10)

1. based on an OSNR Monitoring Method in the band of relevant mixing, it is characterized in that, described method is applied in Optical Signal To Noise Ratio computing system, and described system comprises: Polarization Controller, the input access flashlight of described Polarization Controller; Intrinsic laser device; Coupler, the first input end of described coupler is connected to the output of described Polarization Controller, and the second input of described coupler is connected to the output of described intrinsic laser device; Balanced detector, is connected to described coupler; Electrodymamometer, is connected to described balanced detector; Optical Signal To Noise Ratio calculator, is connected to described electrodymamometer; Described method comprises:

The wavelength controlling the flashlight of channel to be measured is identical with the wavelength of the intrinsic light that described intrinsic laser device produces;

Acquisition first performance number and the second performance number is detected by described electrodymamometer, and described first performance number and described second performance number are sent to described Optical Signal To Noise Ratio calculator, wherein, described first performance number for described flashlight identical with described intrinsic polarisation of light state time the described electrodymamometer performance number that detects, described second performance number be described flashlight vertical with described intrinsic polarisation of light state time, the performance number that described electrodymamometer detects;

Described Optical Signal To Noise Ratio calculator calculates by described first performance number and described second performance number the Optical Signal To Noise Ratio obtained in described channel to be measured.

2. the method for claim 1, is characterized in that, described Optical Signal To Noise Ratio calculator obtains described Optical Signal To Noise Ratio by following formulae discovery:

$\mathrm{OSNR}=10\lg \frac{P_s}{P_n}\&CenterDot;\frac{B_r}{B_n}=10\lg {\left(\frac{<I_{\max }\left(t\right)>-<I_{\min }\left(t\right)>}{2<I_{\min }\left(t\right)>}\right)}^2+10\lg \frac{B_r}{B_n}$

Wherein, OSNR represents Optical Signal To Noise Ratio;

Ps representation signal power;

P _nrepresent noise power;

B _rrepresent the effective bandwidth of described channel to be measured;

B _nnoise equivalent bandwidth;

<I _maxt () > represents the first performance number;

<I _mint () > represents the second performance number.

3. the method for claim 1, is characterized in that, described by described electrodymamometer detection acquisition first performance number and the second performance number, specifically comprises:

Control described flashlight identical with described intrinsic polarisation of light state, and detect described first performance number of acquisition by described electrodymamometer;

Control described flashlight vertical with described intrinsic polarisation of light state, and detect acquisition second performance number by described electrodymamometer.

4. the method for claim 1, is characterized in that, described by described electrodymamometer detection acquisition first performance number with by described second performance number of described electrodymamometer detection acquisition, specifically comprises:

The polarization state of N the described Polarization Controller of adjustment, and then detect the N number of performance number of acquisition by described electrodymamometer, N be more than or equal to 2 positive integer;

Determine that the highest performance number is described first performance number from described N number of performance number;

Determine that minimum performance number is described second performance number from described N number of performance number.

5. the method as described in as arbitrary in claim 1-4, it is characterized in that, before the wavelength of the flashlight of described control channel to be measured is identical with the wavelength of the intrinsic light that described intrinsic laser device produces, described method also comprises:

From multiple channel, select described channel to be measured, described flashlight is by the flashlight of described transmission to be measured.

6. an Optical Signal To Noise Ratio computing system, is characterized in that, comprising:

Polarization Controller, the input access flashlight of described Polarization Controller, described Polarization Controller is for changing the polarization state of described flashlight;

Intrinsic laser device, described intrinsic laser device is for generation of intrinsic light;

Coupler, the first input end of described coupler is connected to the output of described Polarization Controller, and the second input of described coupler is connected to the output of described intrinsic laser device, and described coupler is used for carrying out mixing to described flashlight and described intrinsic light;

Balanced detector, is connected to described coupler, and described balanced detector is used for the light signal of the described balanced detector of input to be converted to the signal of telecommunication, and removes the direct current signal in the described signal of telecommunication;

Electrodymamometer, be connected to described balanced detector, for detecting acquisition first performance number and the second performance number, wherein, described first performance number for described flashlight identical with described intrinsic polarisation of light state time the described electrodymamometer performance number that detects, described second performance number be described flashlight vertical with described intrinsic polarisation of light state time, the performance number that described electrodymamometer detects;

Optical Signal To Noise Ratio calculator, is connected to described electrodymamometer, for obtaining described first performance number and described second performance number from described electrodymamometer, and calculates by described first performance number and described second performance number the Optical Signal To Noise Ratio obtained in described channel to be measured.

7. system as claimed in claim 6, it is characterized in that, described Optical Signal To Noise Ratio calculator is specifically for obtaining described Optical Signal To Noise Ratio by following formulae discovery:

$\mathrm{OSNR}=10\lg \frac{P_s}{P_n}\&CenterDot;\frac{B_r}{B_n}=10\lg {\left(\frac{<I_{\max }\left(t\right)>-<I_{\min }\left(t\right)>}{2<I_{\min }\left(t\right)>}\right)}^2+10\lg \frac{B_r}{B_n}$

Wherein, OSNR represents Optical Signal To Noise Ratio;

Ps representation signal power;

P _nrepresent noise power;

B _rrepresent the effective bandwidth of described channel to be measured;

B _nnoise equivalent bandwidth;

<I _maxt () > represents the first performance number;

<I _mint () > represents the second performance number.

8. system as claimed in claim 7, is characterized in that, described electrodymamometer specifically for:

When described flashlight is identical with described intrinsic polarisation of light state, detects and obtain described first performance number;

When described flashlight is vertical with described intrinsic polarisation of light state, detects and obtain described second performance number.

9. system as claimed in claim 7, is characterized in that, described electrodymamometer specifically for:

By N adjustment of the polarization state of described Polarization Controller, detect and obtain N number of performance number, N be more than or equal to 2 positive integer;

Determine that the highest performance number is described first performance number from described N number of performance number;

Determine that minimum performance number is described second performance number from described N number of performance number.

10. the system as described in as arbitrary in claim 6-9, it is characterized in that, described system also comprises:

Regulate filter, for selecting described channel to be measured from multiple channel, described flashlight is by the flashlight of described transmission to be measured.