JP2624774B2 - Optical fiber fusion splicer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber fusion splicing apparatus, and more particularly to an optical fiber fusion splicer suitable for manufacturing an optical system having an optical fiber closed circuit, such as an optical fiber gyro. The present invention relates to a destination connection device.

[Conventional technology]

Conventionally, permanent connection of an optical fiber is reported in Applied Optics, Vol. 15, No. 3 (1976), pp. 796 to 798 (Applied Optics, vol. 15, No. 3, March 1976). In addition, fusion splicing is widely performed in which the optical axis of an optical fiber is precisely set, and then quartz or multi-component glass constituting the optical fiber is melted and bonded by electric arc discharge. At this time, as described in the above-mentioned document, the optical axis of the optical fiber is generally adjusted by using a light source and a light receiver so as to minimize the loss at the connection point. This is because, in the case of a single mode fiber in particular, the core diameter is as small as 4 to 10 μm and there is a slight eccentricity, so that the connection loss cannot be reduced by visual adjustment based on the outer diameter.

[Problems to be solved by the invention]

Although the above-mentioned prior art is effective for connecting a simple optical fiber line, there are the following problems when an optical fiber closed loop as shown in FIG. 1 is manufactured by fusion splicing. That is, in order to obtain good connection characteristics, it is necessary to cut the end faces of the optical fibers 31 and 32 so as to become flat at substantially right angles as a pre-fusion step. Until the fusion splicing is completed, there is a much smaller gap between the two fibers. This causes reflection at the end face of the optical fiber, and the light propagating through the optical fiber passes through this gap (Fig. 1 At). , Bt) and reflected light (A in the figure)
r, Br). In the case of a quartz optical fiber, interface reflection with air (Fresnel reflection) reaches as much as about 4% of the incident light.

Therefore, the light receiver 40 already detects the reflected light before adjusting the ratio axis of the optical fiber. This is an obstacle in automating the main fusion process in order to maximize the amount of received light. When fusing a polarization-maintaining optical fiber, X,
In addition to adjusting the Y and Z axes, it is necessary to rotate the optical fiber so that the polarization axes of the two fibers coincide with each other. Therefore, the extinction ratio of the optical fiber is measured together with the connection loss. The reflected light is also an error factor in measuring the extinction ratio, and makes it difficult to precisely adjust the polarization axis.

The closed-loop structure of the optical fiber as shown in FIG.
It is used in optical fiber signal processing such as an optical fiber gyro, an optical fiber resonator and the like. SUMMARY OF THE INVENTION An object of the present invention is to provide a means for efficiently producing this optical fiber closed loop structure with good performance.

[Means for solving the problem]

The object is to provide a light supply means for supplying pulsed light to an optical fiber, a light receiving means for receiving the light, a fusion splicing means for fusion splicing between two end faces of the optical fiber, and the light receiving means Control means for controlling the fusion splicing means based on the received light of the optical fiber fusion splicing device, wherein the optical fiber forms a closed loop by the fusion splicing, the light receiving means, This is achieved by providing a means for selectively receiving the transmitted light, out of the transmitted light transmitted between the two end faces and the reflected light reflected at the end face, based on the loop length of the optical fiber.

[Action]

If attention is paid to the difference in the propagation path and the distance between the light transmitted through the fusion splicing point and the light reflected at this point, the two can be identified from the time difference at which the light reaches the light receiver.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 2 shows a fusion splicing apparatus for producing an optical fiber closed loop using the polarization preserving fibers 30, 31, 32, and 33 and the optical splitter 20. The light source comprises a semiconductor laser 12 and this drive circuit 11. The light emitted by the semiconductor laser 12 passes through the polarizer 100 and the polarization rotator (wave plate) 110 and enters the optical fiber 30 by the coupling lens 120. The incident light is split by the optical splitter 20 into an optical fiber 31 (light wave A) and an optical fiber 32 (light wave B). Due to the reflection at the end face of the optical fiber to be fusion spliced, the branched light (light waves A and B) is transmitted light (At and Bt)
And reflected light (Ar and Br). All these light waves are ultimately combined by the optical splitter 20, a portion of which passes through the optical fiber 33 and the analyzer 111 to the light receiver 40.

On the other hand, the electrodes 140 and 141 are high-voltage electrodes for generating an arc, and the intensity and time width of the generated arc are adjusted by the arc control device 150. The optical axis adjustment mechanism 160 uses an optical fiber.
This is a motor-driven exercise device that adjusts the optical axis of the fusion splicing part by rotating in the X, Y, and Z-axis directions. Optical axis controller
170 electrically controls the optical axis adjustment mechanism 160 described above.

The optical axis adjustment operation is achieved by maximizing the amount of light received by the light receiver 40 for the X, Y, and Z axes. The rotation operation for matching the polarization axes of the polarization-maintaining fibers is completed by measuring the extinction ratio with the light receiver 40 while rotating the polarization rotator 110 and the analyzer 111 alternately, and finding the angle at which the extinction ratio becomes maximum. The polarization controller 130 is a control circuit for the polarization rotator 110 and the analyzer 111 for automatically measuring the extinction ratio. Of course, all of the above optical axis adjustment operations can be performed manually.

The control circuit 200 manages the operation of the entire mounting.

As described above, the optical signal detected by the light receiver 40 includes the reflected lights Ar and Br that hinder the optical axis adjustment.
The control circuit 200 generates a control signal for the laser drive circuit 11 and the amount of received light 40 at the timing shown in FIG.

210 is a monitoring device for these timing signals. The laser drive circuit 11 and the light receiver 40 operate only while receiving this control signal. That is, the semiconductor laser 12 generates a light pulse width t with period T, the light receiver 40 is operated by a time width W with a delay time T _D from the optical pulse generator. The delay time T _D and the time width W are determined one by one according to the optical fiber length of the optical fiber closed loop to be manufactured.

Now, let the lengths of the optical fibers 30, 31, 32, 33 be l ₀ , l ₁ , l ₂ ,
and l _3, transmitted light At, Bt, reflected light Ar, when the arrival time at the optical receiver 40 of the Br is calculated on the basis of the generation timing of the laser pulse light following equation is obtained.

The timing shown in FIG. 3 is a case where l ₁ <l ₂ . It was but connexion, as the timing conditions of the light receiver control signals, satisfies the _{T 1 + t <T D <} T 2 ... (4) t <W <T 3 -T 2 ... (5), the transmitted light At, Bt alone Extraction timing can be realized. The timing condition of the laser drive circuit control signal is t <T ₃ −T ₂ (6) T> T ₃ (7).

The above timing conditions (4) to (7) correspond to the control circuit 20
This was achieved by making the optical pulse width t, the period T, the delay time T _D of the light receiving control signal, and the time width W variable as parameters to be input to 0. The oscilloscope 210 visually confirms this timing.

Is usually light Fuaibarupu length l ₂ is the number 100m is light Fuaibajiyairo is _{l 0, l 1, l 3} «l 2. Therefore, as an example, when l ₂ = 400 m, n = 1.5, c = 3 × 10 ⁸ m, and the propagation time τ of the optical fiber loop l ₂ is calculated. It is. Therefore, it can be seen that the processing can be sufficiently performed by the conventional counting circuit using TTL, ECL, or the like.

FIG. 4 shows another embodiment of the present invention. Matching oil having a refractive index equal to or close to that of the optical fiber is dropped between the optical fibers 31 and 32 to be fusion-spliced. Due to the surface tension, the matching oil stays between the two optical fibers and reduces the amount of light reflected at the end face of the fiber, so that the influence of reflection is prevented, and good optical axis adjustment and, consequently, fusion splicing can be realized. Since the matching oil is burned off by the arc discharge, there is no problem in fusion.

〔The invention's effect〕

As described above, according to the present invention, the influence of the reflected light on the end face of the optical fiber can be eliminated, so that the optical fiber can be fusion-spliced while achieving precise optical axis alignment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an optical fiber closed loop system which requires fusion splicing, and shows an example of an object to which the present invention is applied, and FIG.
FIG. 3 shows an example in which the present invention is applied to the production of the optical fiber closed loop system shown in FIG. 3, FIG. 3 shows the timing of control signals for the laser light source and the photodetector in the embodiment of FIG. 2, and FIG. FIG. 8 is a diagram showing another embodiment of the present invention using the above. 10 light source, 11 laser drive circuit, 12 semiconductor laser, 20 optical splitter, 31, 32, 33 optical fiber, 40
Photodetector, 100: Polarizer, 110: Wave plate, 111: Analyzer, 120: Coupling lens, 130: Polarization controller, 140, 14
1 ... arc generating electrode, 150 ... arc control device, 160 ...
… Optical axis adjustment mechanism, 170… Optical axis control device, 200… Control circuit, 210… Monitoring device, 300… Matching oil, 31
0… Matching oil container, 311 …… Matching oil blowing nozzle.

Claims (1)

(57) [Claims] A light supply unit for supplying pulsed light to the optical fiber; a light receiving unit for receiving the light; a fusion splicing unit for fusion splicing between two end faces of the optical fiber; Control means for controlling the fusion splicing means based on the light received by the means, and an optical fiber fusion splicing device comprising: a light emitting element, wherein the optical fiber forms a closed loop by the fusion splicing; A means for selectively receiving the transmitted light, based on a loop length of the optical fiber, out of transmitted light transmitted between the two end faces and reflected light reflected at the end face. Optical fiber fusion splicer.