JP2722666B2 - Crosstalk measuring machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosstalk measuring device for measuring crosstalk indicating polarization maintaining characteristics of a polarization maintaining optical fiber.

<Conventional technology> As an optical fiber sensor and an optical fiber for coherent communication utilizing the interference of light that is recently receiving a trajectory, a polarization maintaining optical fiber (hereinafter, referred to as a polarization maintaining optical fiber having a constant polarization plane).
PM fiber). FIG. 6 shows a cross-sectional structure of a PANDA type PM fiber as an example of such a PM fiber.
As shown in the figure, this PM fiber comprises a core 10a and a clad 10b, and has a stress applying portion 10c provided so as to sandwich the core 10a in the clad 10b. It has a main axis of orthogonal polarization of the book.

Such a PM fiber can propagate two polarization modes, X-polarization and Y-polarization, corresponding to two orthogonal main axes. However, the polarization constant is increased by increasing the propagation constant difference between the two orthogonal polarizations. This is to reduce the amount of optical power coupling between the waves, and crosstalk between two orthogonal polarizations becomes a problem due to the characteristics of the fiber. Therefore, measurement of crosstalk is indispensable for determining the quality of the polarization maintaining optical fiber.

FIG. 7 shows a configuration example of a conventional crosstalk measuring device. As shown in the figure, a PM fiber 10 to be measured is mounted with both ends fixed to a fine movement stage 11, and a light source 12, an excitation fiber 13, a collimation A lens 14, a polarizer 15, and a condenser lens 16 are arranged respectively. Here, the light emitted from the light source 12 is guided by the excitation fiber 13, is collimated by the collimation lens 14, is linearly polarized by the polarizer 15, and then passes through the condenser lens 16. fiber
It is incident on 10. In addition, a collimation lens 17, an analyzer 18, a condenser lens 19, a light receiving fiber 20, and an optical power meter 21 are arranged on the emission side, respectively.
The outgoing light from the PM fiber 10 is collimated by a collimation lens 17 and only a specific polarization component is extracted by an analyzer 18. The light is guided to the power meter 21 and its optical power is measured. The ends of the excitation optical fiber 13 and the light receiving fiber 20 are also fixed to the fine movement stage 11, respectively.

Here, the polarizer 15 is used to make the X-polarized light or the Y-polarized light only enter the PM fiber 10 to be measured.
It must be coincident with either the X axis or the Y axis of the PM fiber 10. On the other hand, the analyzer 18 is used to extract only one of the same polarization as the incident light or the polarization orthogonal to the incident light, and its principal axis direction is also the same as any one of the principal axes of the PM fiber 10 to be measured. Must match direction.

When only the X-polarized light enters the PM fiber 10 to be measured, if the optical power of the X-polarized component of the emitted light is P _X and the optical power of the Y-polarized component is P _Y , the PM to be measured is The crosstalk CT of the fiber 10 is given by CT = 10 log (P _Y / P _X ) [dB].

<Problem to be Solved by the Invention> However, the above-described conventional crosstalk measuring device has the following problems.

As described above, in order to make the principal axis directions of the polarizer 15 and the analyzer 18 coincide with either one of the polarization principal axis directions of the PM fiber 10 to be measured, the power meter 21 is rotated while rotating the polarizer 15 or the analyzer 18. By observing the change in the optical power, the rotational positions of the polarizer 15 and the analyzer 18 must be adjusted, which requires a considerable amount of time.

Further, even if the position of the polarizer 15 is adjusted in this way, it is determined whether the X-polarized light or the Y-polarized light is incident on the PM fiber 10 to be measured. Is not easy.

The quality of the end face state of the measured PM fiber 10 has a great effect on the crosstalk measurement result, but in order to judge the quality, the PM fiber 10 to be measured must be removed from the measuring machine and its end face observed. ,It takes time and effort.

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a crosstalk measuring device that improves the efficiency and reliability of crosstalk measurement.

<Means for Solving the Problems> A crosstalk measuring instrument according to the present invention that achieves the above object,
In a crosstalk measuring instrument that measures crosstalk by inputting polarized light from one end of the held polarization-maintaining optical fiber and measuring the light intensity of the polarized light emitted from the other end, the polarization incident portion is polarized light. And a condensing lens, and the polarization emitting unit includes an analyzer and a collimating lens, and the polarization holding device is provided between the polarizer and the condensing lens or between the analyzer and the collimating lens. An end face observation means for observing the end face of the optical fiber as it is, a main axis angle of the polarization maintaining optical fiber, the polarizer,
And a means for reading the angle of the analyzer.

<Operation> In the crosstalk measuring apparatus having the above-described configuration, since the main axis direction can be determined after observing the input end and the output end of the held pre-held optical fiber by the end face observation means, the crosstalk can be measured. It is easy to match the main axis direction of the polarized light to the main axis direction of the polarization maintaining optical fiber,
Also, it becomes easy to extract a specific polarization from the emitted light,
Workability and reliability can be improved.

<Examples> Hereinafter, the present invention will be described based on examples.

FIG. 1 shows the configuration of a crosstalk measuring device according to one embodiment. The same members as those of the conventional measuring device shown in FIG.

As shown in the figure, the basic configuration of the crosstalk measuring instrument of the present embodiment is the same as that of the crosstalk measuring instrument shown in FIG. 7, but the measuring instrument of the present embodiment serves as an end face measuring means on the incident side. An objective lens 16A for the entrance end face and a camera head 30 for the entrance end face, and an objective lens 17A for the exit end face and a camera head 30 'for the exit end face on the exit side, and signals obtained by these camera heads 30, 30' are monitored. The camera controller 40 and the monitor television 50 are provided.
The objective lens 16A for the incident end face also serves as a condenser lens, and the objective lens 17A for the exit end face also serves as a collimation lens.

In the crosstalk measuring device having such a configuration, the camera head
The images of both ends of the measured PM fiber 10 obtained by 30, 30 'are displayed on the monitor TV 50 via the camera controller 40.
The main axis direction can be confirmed.

The camera heads 30 and 30 'are provided so as to be movable in the direction intersecting the optical path. When the camera heads 30 and 30' are moved out of the optical path at the time of crosstalk measurement, FIG. The crosstalk can be measured similarly to the measuring device shown in FIG. At this time, since the main axis directions of both end faces are confirmed as described above, the measurement becomes easy and accurate.

Next, an example of the incident end camera head 30 will be described with reference to FIG. In the figure, 31 and 32 are mirrors, 33 is a half mirror, 34 is an imaging device, 35 is an illumination light source, 36 is a collimation lens, and the end face 10a of the measured PM fiber 10 is a collimation lens 36, a half mirror 33, and a mirror. It is irradiated with light from the illumination light source 35 via the 31 and the objective lens 16A. Then, the image of the end face 10a formed by the objective lens 16A is sent to the imaging device 34 via the mirrors 31 and 32, where it is converted into an electric signal, and the signal is sent to the camera controller 40.

The emission camera head 30 'may have the same configuration, but it goes without saying that these camera heads are not limited to this.

FIG. 3 shows the configuration of a crosstalk measuring device according to another embodiment. This crosstalk measuring device is basically the same as the measuring device shown in FIG. The same reference numerals are given and duplicate descriptions are omitted.

As shown in the figure, in the crosstalk measuring apparatus of the present embodiment, both end faces of the measured PM fiber 10 are held in the same direction, and the optical system on the incident side and the optical system on the output side are placed on the substrate 60. The camera heads 30 and 30 'are movable in a direction orthogonal to the optical path via rails (not shown) provided on the substrate 60, respectively. This measuring device operates in the same manner as the measuring device shown in FIG. 1 and can observe the end face and measure the crosstalk.

PM fiber to be measured using such a crosstalk measuring machine
FIG. 4 shows a state where the end face of No. 10 was observed. As shown in the figure, the core 10a, the clad 10b, and the stress applying portion 10c were observed with sufficient clarity for practical use. This makes it possible to determine the direction of the main axis of the end face of the PM fiber to be measured, to know the quality of the end face state, and to prevent a crosstalk measurement error due to the end face failure.

In practice, to measure the crosstalk, first, the principal axis angle (indicated by θ in FIG. 4) is measured by observing the incident end face in the above-described direction. Then, as shown in FIG. 5, after adjusting the angle of the polarizer 15 from the relationship between the X polarization and the Y polarization of the polarizer 15 and θ, and then finely adjusting the angle of the polarizer 15, the measurement can be performed. Can be done very efficiently.
At this time, it becomes clear whether X-polarized light is incident or Y-polarized light is incident. It should be noted that the adjustment can be made in the same manner also on the exit side end face.

Conventionally, such a main axis alignment is performed by rotating the polarizer 15 and the analyzer 18 while monitoring the optical power with the optical power meter 21, and the operation took about 2 minutes, but in the present embodiment, When the main axis was aligned as described above, the work was completed in about 40 seconds, about 1/3 of the conventional time.

In the embodiment described above, a camera head provided with an imaging device is used for the end face observation means for observing the end face of the measured PM fiber. However, the present invention is not limited to this. It is also possible to observe directly by visual observation as a configuration similar to a microscope.

<Effects of the Invention> As described above, the crosstalk measuring apparatus according to the present invention has the end face observation means for easily observing the end face of the measured PM fiber as it is, so that the crosstalk measurement efficiency is improved. In addition, reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a crosstalk measuring device according to one embodiment of the present invention, FIG. 2 is a configuration diagram showing an example of the configuration of the camera head, and FIG. 3 is a crosstalk measuring device according to another embodiment. FIG. 4 is an explanatory view showing the observation state of the fiber end face. FIG. 5 is an explanatory view showing the relationship between the main axis angle of the fiber and the polarizer angle at the time of X polarization / Y polarization incidence. FIG. 1 is an explanatory diagram showing an example of a PM fiber, and FIG. 7 is a configuration diagram of a crosstalk measuring device according to a conventional technique. In the drawing, 10 is a PM fiber to be measured, 11 is a fine movement stage, 12 is a light source, 13 is an excitation fiber, 14 is a collimation lens, 15 is a polarizer, 16A is an objective / condenser lens for the incident end face, and 17A is an emission Objective lens and collimation lens for end face, 18 for analyzer, 19 for condensing lens, 20 for light receiving fiber, 21 for optical power meter, 30 for camera head for input end face, 30 'for camera head for output end face, 31, 32 is a mirror, 33 is a half mirror, 34 is an image sensor, 35 is a light source for illumination, 36 is a collimation lens, 40 is a camera controller, and 50 is a monitor television.

Claims (3)

(57) [Claims] 1. A crosstalk measuring device for measuring crosstalk by inputting polarized light from one end of a held polarization-maintaining optical fiber and measuring the light intensity of the polarized light emitted from the other end. The input unit includes a polarizer and a condenser lens, and the polarized light output unit includes an analyzer and a collimator lens, between the polarizer and the condenser lens, or between the analyzer and the collimator lens, An end face observation unit for observing the end face of the held polarization-maintaining optical fiber as it is, and a means for reading the main axis angle of the polarization-maintaining optical fiber, the polarizer, and the angle of the analyzer are provided. A crosstalk measuring device. 2. The measuring instrument according to claim 1, wherein at least a part of members of the end face observing means positioned on an optical path for entering or exiting the end face of the polarization maintaining optical fiber is movable. A crosstalk measuring device that is inserted into an optical path only during observation. 3. The measuring instrument according to claim 1, wherein the lens facing the end face of the polarization maintaining optical fiber for entering or exiting light is used as an objective lens for observing the end face of the end face observing means. A crosstalk measuring device characterized by being used.