CN114487630A - Optical fiber connection method and device for laser noise measurement system - Google Patents
Optical fiber connection method and device for laser noise measurement system Download PDFInfo
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- CN114487630A CN114487630A CN202111610909.5A CN202111610909A CN114487630A CN 114487630 A CN114487630 A CN 114487630A CN 202111610909 A CN202111610909 A CN 202111610909A CN 114487630 A CN114487630 A CN 114487630A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 38
- 238000005259 measurement Methods 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000012360 testing method Methods 0.000 claims abstract description 48
- 230000008878 coupling Effects 0.000 claims description 26
- 238000010168 coupling process Methods 0.000 claims description 26
- 238000005859 coupling reaction Methods 0.000 claims description 26
- 238000003780 insertion Methods 0.000 claims description 10
- 230000037431 insertion Effects 0.000 claims description 10
- 230000003287 optical effect Effects 0.000 description 12
- 230000001427 coherent effect Effects 0.000 description 8
- 238000004891 communication Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 238000001514 detection method Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 241000755266 Kathetostoma giganteum Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/26—Measuring noise figure; Measuring signal-to-noise ratio
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
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Abstract
The invention relates to the technical field of laser testing, in particular to an optical fiber connection method and device for a laser noise measurement system. In the method of the invention, the laser noise measurement system comprises a laser chip, a lens and a test device; the light-emitting waveguide in the laser chip emits laser, and the laser passes through the lens and is connected to the test equipment through the measuring optical fiber; the connecting method is that the lens is connected to the testing equipment through the measuring optical fiber, the measuring optical fiber is connected to the testing equipment after passing through the APC joint and the PC joint in sequence from the lens, wherein the inclined end of the APC joint is adjacent to the PC joint. The method of the invention can weaken reflection, thereby obviously improving the overall performance of the system and obtaining more accurate noise measurement results.
Description
Technical Field
The invention relates to the technical field of laser testing, in particular to an optical fiber connection method and device for a laser noise measurement system.
Background
Lasers used in coherent optical communication require very good noise characteristics. There are 2 typical applications of coherent optical communication technology: 1) data communication transmission, which is the main technical field of optoelectronics, is coherent, which means that signals are extracted at a receiving end of optical communication through a coherent detection technology. The less the noise of the laser used for coherent detection, the clearer the extracted signal; or the original sending signal can be correctly extracted from the weaker signal received by the receiving end. 2) Automatic driving laser ranging, along with the continuous development of automobile automatic driving technology, has proposed higher requirement to the range finding precision and the measuring range of target in front. Coherent light detection is the only means for distance measurement in front of 500 m or more at present, and the resolution of measurement can reach below 1 cm; coherent light detection lasers used for autopilot ranging are also required to have very low intensity noise and phase noise.
With the development of the coherent optical communication technology of the laser, a Noise test Requirement for Intensity Noise (RIN) and Phase Noise (PN) of the laser has arisen. A prior art laser (chip) noise measurement system is shown in fig. 1. In the existing laser noise measurement system, laser emitted by a light-emitting waveguide on a laser chip in the figure enters a measurement optical fiber at a coupling point through refraction of a lens; the optical power coupled into the optical fiber (assuming that the power value is 0dB) is transmitted to the testing equipment almost without loss, the testing equipment theoretically forms certain reflection, and the reflection quantity is between-10 dB and-20 dB in practical engineering, and a typical value is-13 dB for convenience of description.
The reflected optical power of the device is transmitted almost without loss to the coupling point, where a-13 dB backward optical power is obtained, which partly returns through the lens to the light-emitting waveguide on the laser chip, thus affecting the noise characteristics of the laser itself.
Existing modifications incorporate an Isolator (Isolator) in the fiber or between the lenses, which allows only one-way transmission of light, and may eliminate reflections, as shown in fig. 2. However, this improved method has application obstacles: 1) it is theoretically possible to add an isolator between the coupling lenses; however, in engineering practice, an isolator is added between the collimating lens and the coupling lens (typically less than 1 mm in diameter), which requires the construction of a complex and expensive multi-dimensional coupling system. 2) If the isolator is added into the optical fiber, the isolator also has the same reflection problem with the test equipment, and actually, the input ends of a plurality of test equipment are provided with the isolators; in addition, most of the "measurement fibers" used for noise measurement are polarization maintaining (polarization maintaining) fibers, and isolators used for the polarization maintaining fibers are extremely rare in the market.
Disclosure of Invention
The invention provides an optical fiber connection method for a laser noise measurement system aiming at the problems, wherein the laser noise measurement system comprises a laser chip, a lens and a test device; the light-emitting waveguide in the laser chip emits laser, and the laser passes through the lens and is connected to the test equipment through the measuring optical fiber; the connecting method is characterized in that the measuring optical fiber is connected to the testing equipment after passing through an APC joint and a PC joint in sequence from the lens, wherein the bevel end of the APC joint is adjacent to the PC joint.
Further, the APC connector and the PC connector have a distance therebetween.
Furthermore, a medium is arranged between the APC joint and the PC joint, and the reflection loss range formed by the APC joint and the medium is-35 dB to 50 dB.
Furthermore, the insertion loss range formed by mismatching of the APC joint and the PC joint is-2.5-3.5 dB.
Furthermore, the medium is air, and the reflection loss of the APC joint and the air interface is-35-40 dB.
Furthermore, after the laser signal reaches the testing equipment through the PC joint, the reflection loss of the testing equipment is-13 dB, and after the laser returns to the PC joint from the testing equipment, the insertion loss of the laser through the PC joint and the APC joint again is-2.5-3.5 dB, so that the total loss of the laser from the coupling point of the lens and the measuring optical fiber to the coupling point of the testing equipment and then back to the coupling point is-18.39-19.39 dB.
The invention also provides an optical fiber connecting device for the laser noise measuring system, wherein the laser noise measuring system comprises a laser chip, a lens and a test device; the light-emitting waveguide in the laser chip emits laser, and the laser passes through the lens and is connected to the test equipment through the measuring optical fiber; the optical fiber measuring device is characterized by further comprising an APC connector and a PC connector, wherein a connecting 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 testing equipment, the APC connector is positioned on one side close to the coupling point, and meanwhile, the inclined plane end of the APC connector is adjacent to the PC connector.
In the above solution, the present invention mainly adopts the matching of 2 joints to reduce the directional optical power at the coupling point in order to overcome the problem. The difficulty is that the APC connector is beveled and cannot be used with the PC connector in application, but the scheme of the invention mainly overcomes the conventional operation in the traditional application, and obtains the unexpected effect of reducing reflection in noise measurement after matching two connectors which cannot be matched and used originally.
The following describes the effect of the solution according to the invention with reference to typical values:
the transmission medium between the APC joint and the PC joint is air generally, the reflection loss formed by the APC joint and the air interface is-35 dB, the insertion loss formed by the mismatch of the APC joint and the PC joint is-3 dB by default, the reflection loss of the testing equipment is-13 dB after a laser signal passes through the PC joint and reaches the testing equipment, the insertion loss of the laser returning to the PC joint from the testing equipment is-3 dB again, and therefore the total loss of the laser returning to the coupling point from the coupling point of the lens and the measuring optical fiber to the testing equipment is-18.89 dB, and compared with the equipment reflection-13 dB in the existing noise measuring system, the reflection of the method is weakened by about 6dB (to-18.89 dB).
The invention has the beneficial effects that: the reflection can be weakened, so that the overall performance of the system is obviously improved, and a more accurate noise measurement result can be obtained.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 shows a conventional laser noise measurement system.
Fig. 2 is a laser noise measurement system incorporating an isolator.
Fig. 3 is a laser noise measurement system of the present invention.
FIG. 4 is a schematic diagram of the structure of the APC linker.
Fig. 5 is a schematic diagram of an error application.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
As shown in FIG. 3, the connection method of the present invention is mainly to add a connector mismatch formed by an APC (angle Physical connector) connector with an oblique angle and a PC (Physical connector) connector with a flat surface into the measuring fiber. This mismatch of connectors can effectively reduce reflections from the test equipment. The method specifically comprises the following steps:
1. the optical power (assumed to be 0dB) coupled into the optical fiber is transmitted to the APC without loss, the APC and the PC cannot be in close contact with air in the middle, a certain reflection is formed at the interface of the APC and the air and is about-35 dB, if the APC and the air are non-air media, the loss range is usually-35-50 dB, and if the loss is smaller, the effect obtained by the method is better.
Insertion loss (power loss) formed by mismatch of APC and PC is about-3 dB (possible range is-2.5-3.5 dB); then, the signal is transmitted from the PC to the test equipment almost without loss, and the reflection of the test equipment takes a typical value of-13 dB (cumulative loss-16 dB); the reflected light is transmitted back to the PC head with almost no loss.
The mismatch of the PC head and the APC head again creates an insertion loss of about-3 dB (based on measured results), reducing the reflected light back to the coupling point to-19 dB (the possible range values are typically 18.5-19.5 dB). Plus the aforementioned-35 dB reflection, a total of-18.89 dB is reflected.
The method of the present invention reduces the reflection by about 6dB (to-18.89 dB) compared to the device reflection-13 dB in existing noise measurement systems. For the anti-reflection capability of the existing laser, the influence of reflection on the noise of the laser in most cases can be basically eliminated by the method of the invention. Note that the optical power reaching the test equipment is now reduced by about 3dB, which puts higher demands on the sensitivity of the test equipment; but the overall performance of the system is still obviously improved, and a more accurate noise measurement result can be obtained.
For APC and PC connectors used in the present invention, which are themselves sophisticated devices, the design of the present invention has a well established application foundation, as shown in FIG. 4, where one end of the APC joint is beveled, with the standard being 8+/-1 degrees from the ideal plane, as an "8 angle beveled head polished ferrule". The end of the PC connector is a flat-head polishing insert which is actually a paraboloid, so that the unmatched connector cannot be matched for use in practical application. In the invention, aiming at the problem of laser reflection in the laser noise test system, the two unmatched joints can obtain unexpected effects, so that the connecting method and the connecting device are obtained.
The connection mode in the method of the present invention cannot be changed arbitrarily, for example, fig. 5, the direction of the optical fiber splice connection is reversed. Both theoretical calculations and actual measurements are about-15 dB, since the reflections formed by the PC head interface with air can be high. Therefore, the reflected power obtained at the coupling point is-13.54 dB (19 dB back from the test equipment plus-15 dB here). The improvement is not much compared to "get-13 dB reverse optical power at coupling point" in existing noise measurement systems. In addition, the optical power reaching the test equipment is now reduced by about 3dB, which puts higher demands on the sensitivity of the test equipment. In fact, with a measurement system like that of fig. 5, the overall effect becomes worse.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
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; the light-emitting waveguide in the laser chip emits laser, and the laser passes through the lens and is connected to the test equipment through the measuring optical fiber; the connecting method is characterized in that the measuring optical fiber is connected to the testing equipment after passing through an APC joint and a PC joint in sequence from the lens, wherein the bevel end of the APC joint is adjacent to the PC joint.
2. The method of claim 1, wherein the APC connector is spaced from the PC connector.
3. The optical fiber connection method for the laser noise measurement system according to claim 2, wherein a medium is arranged between the APC connector and the PC connector, and the reflection loss formed by the APC connector and the medium is in a range of-35 dB to 50 dB.
4. The optical fiber connection method for the laser noise measurement system according to claim 3, wherein the insertion loss formed by the mismatch of the APC joint and the PC joint is in a range of-2.5-3.5 dB.
5. The method of claim 4, wherein the medium is air, and the reflection loss of the APC joint and air interface is-35-40 dB.
6. The optical fiber connection method for the laser noise measurement system according to claim 5, wherein the reflection loss of the test equipment is-13 dB after the laser signal reaches the test equipment through the PC connector, and the insertion loss of the laser signal which returns to the PC connector from the test equipment and then passes through the PC connector and the APC connector again is-2.5-3.5 dB, so that the total loss of the laser signal from the coupling point of the lens and the measurement optical fiber to the coupling point of the test equipment and then returns to the coupling point is-18.39-19.39 dB.
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 apparatus; the light-emitting waveguide in the laser chip emits laser, and the laser passes through the lens and is connected to the test equipment through the measuring optical fiber; the optical fiber measuring device is characterized by further comprising an APC connector and a PC connector, wherein a connecting 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 testing equipment, the APC connector is positioned on one side close to the coupling point, and meanwhile, the inclined plane end of the APC connector is adjacent to the PC connector.
8. The optical fiber connection device for the laser noise measurement system according to claim 7, wherein the APC connector and the PC connector have a space therebetween, that is, a medium is provided between the APC connector and the PC connector, and the reflection loss formed by the APC connector and the medium is in a range of-35 to 50 dB.
9. The optical fiber connection device for the laser noise measurement system according to claim 8, wherein the insertion loss formed by the mismatch of the APC connector and the PC connector ranges from-2.5 dB to 3.5dB, and the reflection loss of the APC connector and the air interface ranges from-35 dB to 40 dB.
10. The optical fiber connection device for the laser noise measurement system according to claim 9, wherein the reflection loss of the test equipment is-13 dB after the laser signal reaches the test equipment through the PC connector, and the insertion loss of the laser returning from the test equipment to the PC connector and then again through the PC connector and the APC connector is-2.5-3.5 dB, so that the total loss of the laser from the coupling point of the lens and the measurement optical fiber to the coupling point of the test equipment and then returning to the coupling point is-18.39-19.39 dB.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111610909.5A CN114487630A (en) | 2021-12-27 | 2021-12-27 | Optical fiber connection method and device for laser noise measurement system |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111610909.5A CN114487630A (en) | 2021-12-27 | 2021-12-27 | Optical fiber connection method and device for laser noise measurement system |
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| Publication Number | Publication Date |
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| CN114487630A true CN114487630A (en) | 2022-05-13 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111610909.5A Pending CN114487630A (en) | 2021-12-27 | 2021-12-27 | Optical fiber connection method and device for laser noise measurement system |
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| CN (1) | CN114487630A (en) |
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- 2021-12-27 CN CN202111610909.5A patent/CN114487630A/en active Pending
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Effective date of registration: 20240103 Address after: Room 601 and 701, North Block, Yuanxing Technology Building, No.1 Songpingshan Road, High tech Industrial Park (North District), Nanshan District, Shenzhen, Guangdong Province, 518057 Applicant after: Longmet Communication Technology (Shenzhen) Co.,Ltd. Address before: 518057 xinfeitong optoelectronic building, No.8, Keji South 12 road, Nanshan District, Shenzhen City, Guangdong Province Applicant before: NEOPHOTONICS Corp. |