A method and apparatus for fiber optic connection for a laser noise measurement system

Abstract

The present application relates to the technical field of laser testing, and particularly relates to a fiber connection method and device for a laser noise measurement system. In the method, the laser noise measurement system comprises a laser chip, a lens and a test device; a light-emitting waveguide in the laser chip emits laser light, and the laser light passes through the lens and is connected to the test device through a measurement fiber; the connection method is a method of connecting the lens to the test device through the measurement fiber; the measurement fiber is connected to the test device in sequence from the lens, through an APC joint and a PC joint, wherein the inclined end of the APC joint is adjacent to the PC joint. The method can weaken reflection, thereby significantly improving the overall performance of the system and obtaining more accurate noise measurement results.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser testing, in particular to a fiber connection method and device for a laser noise measurement system. BACKGROUND

[0002] Laser applied in coherent optical communication needs very good noise characteristics. Coherent optical communication technology has two typical applications: 1) data communication transmission, which is the main technical field of optoelectronics, and coherence refers to the use of coherent detection technology at the receiving end of optical communication to extract the signal. The smaller the noise of the laser used in coherent detection, the clearer the extracted signal; or the more weak signals received at the receiving end, the original transmitted signal can be correctly extracted. 2) Automatic driving laser ranging, with the continuous development of automatic driving technology, higher requirements are put forward for the ranging accuracy and measurement range of the front target. Coherent light detection is currently the only means for ranging in front of 500 meters or more, and the measurement resolution can reach below 1 centimeter; the coherent light detection laser applied to automatic driving ranging also requires the laser to have very low intensity noise and phase noise.

[0003] With the development of laser coherent optical communication technology, noise testing requirements for the intensity noise (RIN, Relative Intensity Noise) and phase noise (PN, Phase Noise) of the laser have appeared. The existing laser (chip) noise measurement system is as follows Figure 1 The existing laser noise measurement system, the laser emitted by the light emitting waveguide on the laser chip passes through the refraction of the lens and enters the measurement optical fiber at the coupling point; the optical power coupled into the optical fiber (assuming this power value is 0 dB) is transmitted to the test equipment almost without loss, and the test equipment will form a certain reflection in theory. In actual engineering, this reflection is between -10 to -20 dB, and a typical value of -13 dB is taken for convenience of description.

[0004] The reflected optical power of the device is transmitted to the coupling point almost without loss, and the reverse optical power of -13 dB is obtained at the coupling point, which will partially return to the light emitting waveguide on the laser chip through the lens, thereby affecting the noise characteristics of the laser itself.

[0005] The existing improvement method adds an isolator (Isolator) between the optical fiber or the lens, which only allows light to transmit in one direction, which may eliminate the reflection, as follows Figure 2However, the improved method has application barriers: 1) it is theoretically feasible to add an isolator between the coupling lenses; but in engineering practice, adding an isolator between the collimating lens and the coupling lens (generally less than 1 mm in diameter) requires building a complex and expensive multi-dimensional coupling system. 2) If an isolator is added in the optical fiber, the isolator itself will also have the same reflection problem as the test equipment; in fact, the input end of many test equipment is equipped with an isolator; in addition, the "measurement fiber" used for noise measurement is mostly polarization-maintaining (polarization-maintaining) fiber, and isolators for polarization-maintaining fibers are extremely rare on the market. SUMMARY

[0006] The present application is directed to the above problems, and provides a fiber connection method for a laser noise measurement system, wherein the laser noise measurement system comprises a laser chip, a lens and a test equipment; the light-emitting waveguide in the laser chip emits laser light, and the laser light passes through the lens and is connected to the test equipment through a measurement fiber; the connection method is a method of connecting the lens to the test equipment through the measurement fiber, characterized in that the measurement fiber is connected to the test equipment in sequence from the lens, through an APC connector and a PC connector, wherein the beveled end of the APC connector is adjacent to the PC connector.

[0007] Further, the APC connector and the PC connector have a spacing therebetween.

[0008] Further, the APC connector and the PC connector have a medium therebetween, and the reflection loss formed by the APC connector and the medium ranges from -35 to 50 dB.

[0009] Further, the APC connector and the PC connector are mismatched to form an insertion loss ranging from -2.5 to 3.5 dB.

[0010] Further, the medium is air, and the reflection loss of the interface between the APC connector and the air is -35 to 40 dB.

[0011] Further, after the laser signal passes through the PC connector to the test equipment, the reflection loss of the test equipment is -13 dB, and the insertion loss of the laser from the test equipment back to the PC connector and then through the PC connector and the APC connector is -2.5 to 3.5 dB, so that the total loss of the laser from the coupling point of the lens and the measurement fiber to the test equipment and back to the coupling point is -18.39 to 19.39 dB.

[0012] The application also provides a fiber connection device for a laser noise measurement system, the laser noise measurement system comprising a laser chip, a lens and a test device; a light emitting waveguide in the laser chip emits laser light, and the laser light passes through the lens and is connected to the test device through a measurement fiber; characterized in that, the device further comprises an APC connector and a PC connector, a connection point of the lens and the measurement fiber is defined as a coupling point, the APC connector and the PC connector are arranged on the measurement fiber between the coupling point and the test device, and the APC connector is located on one side close to the coupling point, and the beveled end of the APC connector is adjacent to the PC connector.

[0013] In the above scheme, in order to overcome the problem, the application mainly adopts the matching of the two connectors to reduce the directional optical power at the coupling point. The difficulty lies in that the APC connector is usually not used with the PC connector due to the bevel. However, in the scheme of the application, the two connectors that are not matched in the conventional application are matched, and the unexpected effect of reducing reflection in noise measurement is achieved.

[0014] The effect of the scheme of the application will be described below in combination with typical values:

[0015] Generally, the propagation medium between the APC connector and the PC connector is air, and the reflection loss formed by the air interface of the APC connector is-35 dB. It is further assumed that the insertion loss formed by the mismatch of the APC connector and the PC connector is-3 dB. After the laser signal passes through the PC connector to the test device, the reflection loss of the test device is-13 dB. After the laser returns from the test device to the PC connector, the insertion loss of the PC connector and the APC connector is-3 dB again. Thus, the total loss of the laser from the coupling point of the lens and the measurement fiber to the test device and back to the coupling point is-18.89 dB. Compared with the device reflection of-13 dB in the existing noise measurement system, the reflection of the method of the application is reduced by about 6 dB (to-18.89 dB).

[0016] The application has the beneficial effect of reducing reflection, thereby significantly improving the overall performance of the system and obtaining more accurate noise measurement results. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0018] Figure 1 It is the existing laser noise measurement system.

[0019] Figure 2 For the laser noise measurement system of the isolator.

[0020] Figure 3 For the laser noise measurement system of the application.

[0021] Figure 4 For the structure diagram of APC joint.

[0022] Figure 5 For the schematic of the wrong application mode. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0024] As Figure 3 shown, the connection method of the application mainly adds a mismatch of connectors by connecting an APC (Angle Physical Connector) connector with an angle and a PC (Physical Connector) connector with a plane in the measurement optical fiber. The mismatch of the connectors can effectively weaken the reflection caused by the test equipment. Specifically:

[0025] 1. The optical power coupled into the optical fiber (assuming 0 dB) is almost losslessly transmitted to the APC, and the APC and the PC cannot be in close contact with air in the middle, and the interface between the APC and the air will form a certain reflection of about -35 dB. If it is a non-air medium, the loss range is usually -35-50 dB. The smaller the loss is, the better the effect of the method of the application can achieve.

[0026] 2. The mismatch of the APC and the PC forms an insertion loss (power loss) of about -3 dB (the possible range is -2.5-3.5 dB); then, the light is almost losslessly transmitted from the PC head to the test equipment, and the reflection of the test equipment takes a typical value of -13 dB (the cumulative loss is -16 dB); the reflected light is almost losslessly transmitted to the PC head in reverse.

[0027] 3. The mismatch of the PC head and the APC head forms an insertion loss of about -3 dB (based on the actual measurement result), so that the reflected light returned to the coupling point is reduced to -19 dB (the possible range value is usually 18.5-19.5 dB). Adding the aforementioned -35 dB reflection, the total reflection is -18.89 dB.

[0028] Compared with the device reflection-13dB in the existing noise measurement system, the reflection of the method of the present application is reduced by about 6dB (to-18.89dB). For the anti-reflection ability of the existing laser, the influence of the reflection on the laser noise can be basically eliminated by the method of the present application in most cases. Note that the optical power reaching the test device at this time will be reduced by about 3dB, which will require higher sensitivity of the test device; but the overall performance of the system will still be significantly improved, and more accurate noise measurement results can be obtained.

[0029] For the APC and PC connectors used in the present application, they are mature devices themselves, so that the design of the present application has a mature application basis, such as Figure 4 As shown, one end of the APC connector is beveled, and the standard is 8+ / -1 degrees away from the ideal plane, which is an "8° angle beveled polished ferrule". The end of the PC connector is a "flat polished ferrule", which is actually a parabolic surface, so in practical application, mismatched connectors will not be matched for use. In the present application, for the problem of laser reflection in the laser noise test system, these two mismatched connectors unexpectedly achieve good results, so the connection method and device of the present application are obtained.

[0030] The connection method in the method of the present application cannot be changed at will, for example Figure 5 , the direction of the fiber connector connection is reversed. Since the reflection formed by the interface between the PC head and the air will be high, the theoretical calculation and actual measurement value are both about-15dB. Therefore, the reflected power obtained at the coupling point is-13.54dB (the-19dB returned from the test device plus-15dB here). Compared with the "obtaining-13dB of reverse optical power at the coupling point" in the existing noise measurement system, the improvement is not great. In addition, the optical power reaching the test device at this time will be reduced by about 3dB, which will require higher sensitivity of the test device. In fact, the comprehensive effect will become worse by using the measurement system as shown in Figure 5

[0031] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. An optical fiber connection method for a laser noise measurement system, the laser noise measurement system comprising a laser chip, a lens, and a test device; a light emitting waveguide in the laser chip emits laser light, and the laser light passes through the lens and is connected to the test device through a measurement optical fiber; the connection method is a method of connecting the lens to the test device through the measurement optical fiber, characterized in that, The measuring optical fiber is connected to the test device in turn through the lens, the APC connector and the PC connector, wherein the beveled end of the APC connector is adjacent to the parabolic end of the PC connector, and wherein the mismatch between the APC connector and the PC connector is configured to weaken the reflection caused by the test device.

2. The method of claim 1, wherein, The APC connector and the PC connector have a spacing therebetween.

3. The method of claim 2, wherein the optical fiber connection is made by, The APC connector and the PC connector have a medium therebetween, and the APC connector and the medium form a reflection loss ranging from -35 to 50 dB.

4. The method of claim 3, wherein the optical fiber connection is made by, The APC connector and the PC connector form an insertion loss ranging from -2.5 to 3.5 dB.

5. The method of claim 4, wherein the optical fiber connection is made by, When the laser signal passes through the PC connector to the test device, the reflection loss of the test device is -13 dB, and the laser from the test device back to the PC connector again passes through the PC connector and the APC connector with an insertion loss of -2.5 to 3.5 dB, so that the total loss of the laser from the coupling point of the lens and the measuring optical fiber to the test device and back to the coupling point is -18.39 to 19.39 dB.

6. The method of claim 5, wherein the optical fiber connection is made by, The APC connector and the PC connector are further included, and the coupling point of the lens and the measuring optical fiber is defined as a coupling point, the APC connector and the PC connector are arranged on the measuring optical fiber between the coupling point and the test device, the APC connector is located on one side close to the coupling point, and the beveled end of the APC connector is adjacent to the parabolic end of the PC connector; and the mismatch between the APC connector and the PC connector is configured to weaken the reflection caused by the test device.

7. An optical fiber connection device for a laser noise measurement system, the laser noise measurement system comprising a laser chip, a lens and a test device; a light emitting waveguide in the laser chip emits laser light, the laser light passes through the lens and is connected to the test device through a measurement optical fiber; characterized in that, The APC connector and the PC connector have a spacing therebetween, i.e., the APC connector and the PC connector have a medium therebetween, and the APC connector and the medium form a reflection loss ranging from -35 to 50 dB.

8. An optical fiber connection device for a laser noise measurement system according to claim 7, wherein, The APC connector and the PC connector form an insertion loss ranging from -2.5 to 3.5 dB, and the APC connector and the air interface form a reflection loss ranging from -35 to 40 dB.

9. An optical fiber connection device for a laser noise measurement system according to claim 8, wherein, When the laser signal passes through the PC connector to the test device, the reflection loss of the test device is -13 dB, and the laser from the test device back to the PC connector again passes through the PC connector and the APC connector with an insertion loss of -2.5 to 3.5 dB, so that the total loss of the laser from the coupling point of the lens and the measuring optical fiber to the test device and back to the coupling point is -18.39 to 19.39 dB.

10. An optical fiber connection device for a laser noise measurement system according to claim 9, wherein, ​

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