CN109039442A - The calibrating installation and calibration method of Optical Return Loss - Google Patents

Abstract

The invention provides a test device and a test method for optical return loss, the test device comprises a coupler (11), an isolator (12), a variable optical attenuator (13) and an optical fiber (14) with a preset length; The coupler (11) includes a trunk port (110), a first branch port (111) and a second branch port (112), the first branch port (111) is connected to the input end of the isolator (12), The output end of the isolator (12) is connected to one end of the variable optical attenuator (13), and the other end of the variable optical attenuator (13) is connected to the second branch port (112) through a preset length of optical fiber (14) connected; the light splitting ratio of the first branch and the second branch is 1:N. The optical return loss verification device of the present invention has a simple structure, and is easy to measure the optical return loss value of the verification device based on a light source and an optical power meter, and can simulate a variable optical echo suitable for optical time domain reflectometer measurement. Loss value, the optical return loss parameter for calibrating the optical time domain reflectometer.

Description

Optical return loss testing device and testing method

technical field

The invention relates to the technical field of communication, in particular to a test device and a test method for optical return loss.

Background technique

With the increasing complexity of optical fiber communication networks, there are more and more events such as reflection and loss on optical fiber links, and the requirements for the ability of Optical Time Domain Reflectometer (OTDR) to identify events are also more stringent. , it is required that the optical time domain reflectometer can accurately measure the optical return loss of the reflection event.

However, the current JJG 959-2001 "Verification Regulations for Optical Time Domain Reflectometer" does not specify the verification method and device for optical return loss. After consulting the literature, there is no verification device for optical return loss of optical time domain reflectometer. Some optical return loss verification devices are only for optical return loss testers, not for optical time domain reflectometers.

For the optical return loss parameters of the optical time domain reflectometer, there is currently a lack of reliable metrological verification devices to verify the optical return loss measurement capability and measurement accuracy of the optical time domain reflectometer, resulting in the inability to carry out effective traceability of the value.

Contents of the invention

In view of this, the present invention provides a verification device for optical return loss to solve the problem that optical return loss parameters of an optical time domain reflectometer cannot be measured and verified.

The invention provides a test device for optical return loss, the test device comprises a coupler (11), an isolator (12), a variable optical attenuator (13) and an optical fiber (14) with a preset length;

The coupler (11) comprises a trunk port (110) receiving optical input, a first branch port (111) and a second branch port (112), the first branch port (111) and the isolator (12) The input end is connected, the output end of the isolator (12) is connected with one end of the variable optical attenuator (13), and the other end of the variable optical attenuator (13) is connected with the second branch port (112) through a preset length Optical fiber (14) connects;

The light splitting ratio of the first branch and the second branch is 1:N.

The present invention also includes a test method for optical return loss, including;

Input the incident light to be measured from the equipment to be tested to the trunk port of the coupler (11) in the verification device of optical return loss of the present invention, and receive the incident light to be measured from the trunk port of the coupler (11) the return light;

Obtain the optical return loss measurement value of the equipment under test based on the power of the incident light and return light to be measured;

Calibrate the measured value of the optical return loss with the optical return loss R of the verification device with traceable value.

The optical return loss verification device invented has a simple structure, and it is easy to measure the optical return loss R value of the verification device based on a light source and an optical power meter. The arbitrary variable optical return loss value can meet the metrological verification and calibration of optical time domain reflectometer or other instrument optical return loss parameters. After testing, the uncertainty of optical return loss reaches 0.7dB (inclusion factor k=2).

Description of drawings

Fig. 1 is the testing device of optical return loss of the present invention and the OTDR to be checked;

Figure 2 is a trace diagram of optical return loss measurement.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the present invention provides a test device for optical return loss, which test device includes a coupler (11), an isolator (12), a variable optical attenuator (13) and a preset length optical fiber (14);

The coupler (11) comprises a trunk port (110) receiving optical input, a first branch port (111) and a second branch port (112), the first branch port (111) and the isolator (12) The input end is connected, the output end of the isolator (12) is connected with one end of the variable optical attenuator (13), and the other end of the variable optical attenuator (13) is connected with the second branch port (112) through a preset length Optical fiber (14) connects;

The light splitting ratio of the first branch and the second branch is 1:N.

In order to display the trace of the optical fiber back Rayleigh scattering signal more clearly on the OTDR (2) to be calibrated, and at the same time be able to simulate a wider range of optical return loss values, preferably 7≤N≤9.

Further, in order to completely display the trace of the fiber Rayleigh backscattering signal except the initial saturation region on the OTDR to be calibrated, and at the same time reduce the attenuation introduced by the fiber link, preferably 2km≤preset length≤4km.

In Fig. 1, it is the trunk port (110) of the emission light input coupler (11) of the schooled OTDR (2), which is divided into two paths through the coupler (11), and the upper branch passes through the optical fiber (14), variable optical attenuation After the isolator (13), it is blocked at the isolator (12) and cannot return to the OTDR (1) to be calibrated. After the lower branch passes through the isolator (12), the variable optical attenuator (13) and the optical fiber (14), the coupler (11) returns to the OTDR (2) to be calibrated to form an optical echo.

It should be noted that “2” in FIG. 1 may be the calibrated OTDR, or other instruments capable of measuring optical return loss parameters, which is not limited in the present invention.

The optical return loss measurement trace diagram monitored by the OTDR is shown in Figure 2. The flat part on the trace diagram is the received light returned to the OTDR by the Rayleigh backscattering of the optical fiber. This part of the light has gone through a round trip, twice The path of the fiber length, so when the OTDR calculates and draws the trace diagram, it divides the total travel by 2 and displays it on the trace diagram. Therefore, when the lower branch light of the coupler (11) passes through the isolator (12), the variable optical attenuator (13) and the optical fiber (14, such as 3km) and returns to the OTDR to form an optical echo, at the middle position of the trace (at about 1.5km) a reflection peak is formed, and the OTDR will automatically measure the optical return loss measurement value R _OTDR of the reflection peak.

Let the insertion loss of the first branch be IL ₁ , the insertion loss of the isolator be L _s , the attenuation of the variable optical attenuator be L _a , the insertion loss of the second branch be IL ₂ , the fiber link of the preset length attenuation to L _f ;

Then the optical return loss value of the verification device is R=IL ₁ +L _s +L _a -IL ₂ -L _f .

IL ₁ , L _s , L _a , IL ₂ , and L _f can all be measured by light source and optical power meter. In this way, the R value of the verification device according to the present invention can be used to calibrate the optical return loss parameter R _OTDR of the optical time domain reflectometer.

Specific instructions are given below:

When using insertion loss and attenuation to calculate the optical return loss R value of this application, first consider that the loss experienced when the upper branch of the coupler is transmitted to the end of the optical fiber includes: the insertion loss IL ₂ of the second branch on the coupler, the optical fiber link The path attenuation L _f , IL ₂ and L _f can be measured by light source and optical power meter, and the values can be traced to the national standard of optical power. The injected optical power when the upper branch of the coupler is transmitted to the end of the fiber is

P _in ＝P _OTDR –IL ₂ -L _f (1)

In the formula: P _in is the injected optical power when the upper branch of the coupler is transmitted to the end of the fiber, in dBm; P _OTDR is the initial power of the OTDR emitted light, in dBm; IL ₂ is the second branch on the coupler Insertion loss, in dB; L _f is fiber link attenuation, in dB.

In addition, the loss experienced when the lower branch of the coupler is transmitted to the end of the fiber includes: the insertion loss IL ₁ of the first branch on the coupler, the insertion loss L _s of the optical isolator, the attenuation L _a introduced by the variable optical attenuator, IL ₁ , L _s and L _a can all be measured by light source and optical power meter, and the values can be traced to the national standard of optical power. The return optical power when the lower branch of the coupler is transmitted to the end of the fiber is

P _R ＝P _OTDR –IL ₁ -L _s -L _a (2)

In the formula: P _R is the echo optical power when the light from the lower branch of the coupler is transmitted to the end of the fiber, in dBm; IL ₁ is the insertion loss of the first branch on the coupler, in dB; L _s is the optical isolator Insertion loss, the unit is dB; L _a is the attenuation introduced by the variable optical attenuator, the unit is dB.

Finally, the optical return loss R value of the verification device of this application can be obtained by subtracting the echo optical power from the injected optical power at the end of the optical fiber, expressed by formula (3):

R＝IL ₁ +L _s +L _a -IL ₂ -L _f (3)

During calibration, the optical return loss measurement value R _OTDR measured by the OTDR (2) to be calibrated is subtracted from the R value to obtain the indication value error of the optical return loss. It can be known from formula (3) that the dynamic range of R is the same as that of L _a , by adjusting the attenuation value of the variable optical attenuator, different reference values of optical return loss can be obtained, that is, different gears can be realized The error of the optical return loss indication is calibrated. The height of the reflection peak in Figure 2 also reflects the situation when adjusting the attenuation of the variable attenuator to obtain different reference values of optical return loss.

The present invention also includes a test method for optical return loss, including;

Input the incident light to be measured from the equipment (2) to be tested to the trunk port of the coupler (11) in the verification device of the optical return loss of the present invention, and receive the test light from the trunk port of the coupler (11) Measure the return light of the incident light;

Obtain the optical return loss measurement value of the equipment under test based on the power of the incident light and return light to be measured;

Calibrate the measured value of the optical return loss with the optical return loss R of the verification device with traceable value.

The verification device and verification method of the present invention can simulate any variable optical return loss value suitable for optical time domain reflectometer measurement within a certain range, satisfying the measurement verification and calibration of optical time domain reflectometer optical return loss parameters. After testing, the uncertainty of optical return loss reaches 0.7dB (inclusion factor k=2).

The technical advantage of the verification device of the present invention is embodied in that the simulated optical return loss reflection peak is visually displayed on the optical time domain reflectometer measurement trace, with good repeatability and high stability.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the technical solutions of the present invention are all Should be included within the protection scope of the present invention.

Claims (6)

1. a kind of calibrating installation of Optical Return Loss, which is characterized in that the calibrating installation includes coupler (11), isolator (12), the optical fiber (14) of variable optical attenuator (13) and preset length；

The coupler (11) includes the main line port (110) for receiving light input, first branch port (111) and second branch end Mouthful (112), the first branch port (111) are connected with the input terminal of the isolator (12), the isolator (12) it is defeated Outlet is connected with the one end of the variable optical attenuator (13), the other end of the variable optical attenuator (13) with described second Road port (112) is connected by the optical fiber (14) of preset length；

The splitting ratio of the first branch and the second branch is 1:N.

2. calibrating installation according to claim 1, which is characterized in that 7≤N≤9.

3. calibrating installation according to claim 1, which is characterized in that 2km≤preset length≤4km.

4. calibrating installation according to claim 1, which is characterized in that

The insertion loss for enabling the first branch is IL₁, the insertion loss of the isolator is L_s, the variable optical attenuator Decay to L_a, the insertion loss of the second branch is IL₂, the optical fiber link of the preset length decays to L_f；

The then Optical Return Loss R=IL of the calibrating installation₁+L_s+L_a-IL₂-L_f。

5. calibrating installation according to claim 4, which is characterized in that by adjusting L_aNumerical value obtain different R values.

6. a kind of calibration method of Optical Return Loss, which is characterized in that the method includes；

It will be from the calibrating for being input to any Optical Return Loss of claim 1 to 5 by the incident light to be measured of calibration equipment (2) The main line port of the coupler (11) in device, and the incidence to be measured is received from the main line port of the coupler (11) The return light of light；

Power based on the incident light to be measured and the return light is obtained by the Optical Return Loss measured value of calibration equipment；

With the calibrating installation there is the Optical Return Loss R of magnitude tracing to calibrate the Optical Return Loss measured value.