JPS61270637A - Measuring method for back scattering loss of optical fiber - Google Patents

Abstract

PURPOSE:To improve the accuracy of the backward scattering loss measurement of an optical fiber to be measured by connecting one terminal of the optical fiber to be measured to the light projection end of a measuring instrument side in an optimum state and optimizing a lightreception level and excitation condition. CONSTITUTION:The axial interval between the light projection end 9 of an optical cord 4 and one end 10 of the optical fiber is made constant so as to position both ends in an optimum state. The axial interval between the ends 9 and 10 is set to a fine distance of about tens of mum so as to reduce the loss of their connection. Then, a controller 15 refers to an electric signal proportional to the lightreception intensity of light pulses lightreceived 13 through a light pulse generator 1, an optical directional coupler 3, etc., and then moves a holder 11 vertically so that the lightreception intensity is maximum. The connection between the ends 9 and 10 is so adjusted that the intensity of transmitted light from the other end 14 of the optical fiber 8 is maximum, thereby minimizing the loss of the connection between the ends 9 and 10. Further, the excitation of the cord 4 is transmitted to the fiber 8 without any variation. Further, the lightreception level of the controller 15 becomes high and its referring operation is performed easily and automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Application This invention relates to an improvement in a method for measuring backscattering loss of an optical fiber.

(b) Prior Art Conventionally, a backscattering loss measurement method has been known as one of the methods for measuring optical loss of an optical fiber.

FIG. 1 shows a schematic diagram of a conventional backscattering loss measurement. In FIG. 1, numeral 1 is a light/ξ lux generator;
For example, it consists of a semiconductor laser and its driving circuit. The optical pulses generated by the optical pulse generator 1 pass through the optical coat 2 and are applied to the optical directional coupler 3. Optical directional coupler 3
provides the optical pulses via the optical coat 2 to the optical connector 5 via the optical cord 4, and sends the light incident from the optical coat 94 side to the light receiver 7 via the optical cord 6. Optical connection part 5
is a portion where the light output end 9 of the optical cord 4 and one end 10 of the optical fiber 8 are optically connected, and the light pulses from the optical cord 4 are input to the one end 10 of the optical fiber 8.

Then, the Rayleigh backscattered light and Fresnel reflected light detected from the four ends 10 are optical code 4, optical directional coupling: (K3
This 111115 light is received by the light receiver 7 through
: The loss characteristics of the optical fiber are known based on rl.

The above-mentioned backscattering [1-loss measurement method] is an effective method that not only can easily detect the breaking point of the optical fiber, but also can measure loss crystallinity with no significant difference from the transmission method.

In addition, the city law requires that the loss dependence in the optical fiber direction can be measured, that it can be measured without damaging the optical fiber, and that in the transmission method, reference foreshadowing is used to compensate for the wavelength dependence of the measuring instrument. However, it is not necessary.

(c) Problems to be Solved by this Invention The backscattered loss measuring method with the conventional configuration as shown in Figure 2] 1. Backscattered light such as Rayleigh scattered light and Lunel reflection q dimension light that cannot be measured is very large. The problem is that it is difficult to measure with high precision because the Therefore, conventionally, we used a repeating pulse light source with a high slope as a light source, and performed IL equalization processing on the electrical signal photoelectrically converted by the photoreceiver 7. Attempts have been made to change the direction by -L. In order to improve accuracy, the optical connection section 5 becomes an important element. That is, the likely loss in the optical connection part 5 is
This not only affects the signal, but also the excitation conditions of the normal driver to be measured. In order to improve the light reception level, it is necessary to use a precise groove to optimize the connection shape of the optical connection section 17], and to eliminate the influence of the spliced fiber on the excitation conditions of the fiber under test. Although it is done to obtain appropriate excitation conditions by inserting an appropriate excitation penalty in 1'4, the only thing to know about it is that the connection state and excitation conditions are confirmed by weak 71i: Backscattered light O'. Because of this, it was not possible to accurately understand the data, and it took a long time to understand it due to extensive averaging processing, etc.

This invention optimizes the connection between one end of the optical fiber to be measured and the light emitting end of the measuring instrument to optimize the received light level and excitation conditions, thereby improving the accuracy of backscattering loss measurement of the optical fiber. It is an object of the present invention to provide a force method for measuring backscattering loss of an optical fiber, which can be used to measure the backscattering loss of an optical fiber.

(b) Means for solving the problem The positioning of the end of the optical fiber to be measured and the light emitting end on the measuring instrument side includes the step of IM positioning the end of the optical fiber to be measured and the light emitting end at a constant axial distance; a step of receiving the light pulse transmitted through the optical fiber from the other end of the optical fiber to be measured; and monitoring the received light intensity of the optical fiber in a direction perpendicular to the axial direction so that the received light intensity is maximized. (11) positioning one end of the optical fiber to be measured by moving it relative to the light emitting end on the measuring instrument side;

(e) Positioning of the end of the optical fiber to be measured and the light emitting end on the measuring instrument side is done by monitoring the light pulses transmitted from the light emitting end to the optical fiber to be measured using the light receiving j7 so that the light receiving level is maximized. Therefore, the connection loss at both ends can be minimized, and the excitation line fl to the optical fiber to be measured can be optimized.

(F) Embodiment FIG. 1 shows a schematic system configuration diagram for implementing the backscattering loss measuring method of the present invention. In FIG. 1, the same parts as those in FIG. 2 are indicated with the same symbol, and their explanation will be omitted. A holder 11 is attached to the light output end 9 of the optical cord 4 constituting the optical connection section 5 in FIG.
A holder 12 is attached to each. Several light receivers 13 are arranged at the other end 14 of the optical fiber 8, and the light pulses transmitted through the optical fiber 8 are received by the light receivers 13, where they are converted into electrical signals proportional to the received light intensity. , to the controller 15 via the line l.
0 axis to position the ends 9 and 10 relative to each other to maximize the level of light received. □In order to optimally position the light output end 9 of the optical coat "4" and one end 10 of the optical fiber 8, first, the distance between the ends 9 and 100 in the axial direction is made constant. Since this corresponds to the end of the optical fiber that is the core of For axial alignment of the ends 9, 100, for example, slide both fibers axially over the grooves as holders 11, 1.2, and align their ends 9, 1.
1. In a contact type using a fiber stopper ξ such as that used in a fusion splicer, the fiber stopper ξ is fixed when it comes into contact with the fiber stopper. The 15th method, its song, and the method of optical non-contact are known.

Next, the light/glucose generator 1, the tail directional coupler 3, the light
The light received by the light receiver 13 through the fiber 8 sequentially is ? The controller 15 moves the holder 11 to the vertical nozuki a] so that the received light intensity is the maximum, and the controller 15 moves the light intensity to the maximum output. When Iq- is obtained, the holder 11 is moved by 1.11-.

However, in I~, the connection between the ends 9 and 10 can be adjusted so that the light intensity of the transmitted light from the other end 14 of the optical fiber 8 is maximized, so that the connection loss at the ends 9 and 10 is minimized, and
The excitation of the optical fibers 1-4 is transmitted to the optical fiber 8 with the least fluctuation. Note that the movement of the holder 11 is several μy.
This is done with an accuracy of about n, and since the received light level referenced by the controller 15 is transmitted light, it is at a higher level than the backscattered light, and the reference can be easily, stably, and automatically performed. 2. Mechanisms for vertical movement of the holder 11 are conventionally known in optical fiber fusion splicing machines, and various methods such as two-direction linear fine movement, stress strain, and electrostrictive elements are utilized.

In the above embodiment, the holder 11 was moved by the controller 15, but the positions of the ends 9 and 10 can also be determined relative to each other by moving the holder 1-2.

(g) Effects This invention minimizes the connection loss between the optical fiber end and the measuring instrument side light emitting end, and also allows both ends to be positioned (+'r) under optimal excitation conditions. It is possible to perform highly accurate loss measurements with an improved light reception level in scattering loss measurements.In comparison to the conventional method, where it is difficult to determine the connection status at both ends of III only by using backscattered light, this method Since the measurement method refers to the high level of light received transmitted through the optical fiber, positioning is easy and labor-saving can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a measurement system showing an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a conventional backscattering loss measurement method. I... Optical Hals generator, 2.4.6... Optical code 1.
゛, 3... Optical directional coupling 8K, 5 Optical connection section, 7,
13...Receiver, 8...Light) "Aiba, 9
. . . Light output end of optical fiber 1.゛, 10. One end of optical fiber, 1. , l, 12... holder, 14...
The other end of the optical fiber, 15...controller. Special applicant Sumitomo Tunki Industries, Ltd. (5 others) Tail 1 figure Tail 2 concave

Claims (1)

[Scope of Claims] A light pulse is inputted into one end of the optical fiber to be measured from a light emitting end on the measuring device side, and Rayleigh backscattered light and Fresnel reflected light due to the light pulse are detected from the one end, and the optical fiber to be measured is In the method for measuring backscattering loss, the positioning of the end of the optical fiber to be measured and the light emitting end on the measuring device side includes the step of positioning the end and the light emitting end at a constant distance in the axial direction; a step of receiving the light pulse transmitted through the measurement optical fiber from the other end of the optical fiber to be measured and monitoring the received light intensity; A method for measuring backscattering loss of an optical fiber, comprising the step of positioning the end of the measuring optical fiber by moving it relative to the light emitting end on the measuring instrument side.