JPH06229716A - Method for estimating positional shift between optical connectors and method for inspecting characteristics of guide pinhole of optical connector - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide a method for estimating a relative positional deviation between optical connectors at the time of coupling from a connection loss value. [Structure] The connection loss value between the optical fibers (7, 8) of each pair that are abutted at the time of connector coupling is obtained, and the core axis deviation between the cores of the optical fibers of each pair is obtained from the connection loss value. Further, the eccentricity of the core of each optical fiber in each optical connector (1, 2) is measured, and the position of the other optical connector is virtually shifted with respect to one optical connector, and at that time, each pair of optical fibers The core axis deviation between the cores is determined from the core eccentricity measurement value. Then, a virtual positional shift is calculated when the core axial shift obtained from the connection loss value and the above-mentioned virtual core axial shift best match. The present invention is characterized in that the virtual positional deviation thus obtained is estimated as the relative positional deviation between the actual optical connectors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-fiber optical connector used for coupling a plurality of optical fibers in the field of optical communication and the like, and more particularly, to a relative positional deviation between the coupled optical connectors. The present invention relates to a method for estimating and a method for inspecting characteristics of guide pin holes of an optical connector.

[0002]

2. Description of the Related Art Factors of connection loss in an optical connector include axial misalignment between cores of optical fibers, angular misalignment between optical fibers, end face gap between optical connectors, structural mismatch between optical fibers, etc. In the single-mode optical fiber connector of, the axial misalignment between the optical fiber cores (hereinafter,
This is called "core axis deviation"). Generally, the connection loss value α (dB) caused by the core axis deviation Δ (μm)
Can be expressed by the following equation.

[0003]

[Equation 1]

Here, C is a constant determined by the structure of the optical fiber, and is about 0.
It takes a value of 19. Thus, there is a clear correlation between the splice loss value and the core axis deviation, and if the splice loss value is known,
The core axis deviation can be obtained.

The main cause of the core axis deviation is the processing accuracy of the fiber hole of the optical connector. However, in the region where the amount of eccentricity required for a normal connector for single-mode optical fiber is about 2 μm or less, there is almost no correlation between the measured eccentricity of the fiber hole and the actual splice loss value. This is because the eccentricity of the core of the optical fiber and the eccentricity of the fiber hole do not always match. That is, there is always 1 between the fiber hole of the optical connector and the optical fiber inserted into the fiber hole.
Since a clearance of about μm is required and the core of the optical fiber itself is eccentric about 0.5 μm with respect to the center of the outer diameter, even if the fiber hole is not eccentric,
Core axis misalignment may occur.

In recent years, a technique for measuring the eccentricity of the core of the optical fiber after attaching the optical fiber to the optical connector has been developed, and it has become possible to evaluate the relationship between the measured value of the core eccentricity and the splice loss value. .

However, there is still no good correlation between the core eccentricity measurement and the splice loss value.

For this reason, conventionally, it has not been performed to calculate the relative positional deviation between the optical connectors at the time of coupling from the connection loss value.

[0009]

When the optical connectors are coupled to each other, the guide pins are inserted into the two guide pin holes formed in the coupling end faces of the respective optical connectors to position them. It is common.

However, in reality, there is often a mismatch of 1 to 2 μm between the guide pin holes facing each other when the connectors are coupled, and the clearance between the guide pin holes is about 1 μm. Further, the shape of the guide pin hole and the guide pin are not necessarily perfect circles.

Considering such a situation, the optical connector is rarely accurately coupled in the positional relationship as designed,
It can be said that there is always a risk of causing an error of 1 to 2 μm in order to estimate the core axis deviation when the optical connector is coupled from the measured value of the core eccentricity.

However, in the past, since the splice loss analysis was performed on the premise that the optical connector was accurately positioned, no correlation was found between the splice loss value and the core eccentricity measurement value. Therefore, the relative displacement between the optical connectors cannot be obtained from the connection loss value.
In addition, the conventional way of thinking has not been able to explain any variation in connection loss or attachment.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for estimating a relative positional deviation between optical connectors at the time of coupling from a connection loss value. In addition, the present invention enables inspection of guide pin hole characteristics based on the estimated displacement.

[0014]

In order to achieve the above-mentioned object, the invention according to claim 1 relates to a relative relation between both optical connectors when the optical connectors to which a plurality of optical fibers are attached are coupled. In a method of estimating a general positional deviation, a first step of obtaining a connection loss value between optical fibers of each pair that are abutted at the time of connector coupling, and an axial deviation between cores of the optical fibers of each pair from the connection loss value. And a third step of measuring the eccentricity of the core of each optical fiber in each optical connector, and the position of the other optical connector is virtually shifted with respect to one optical connector, and each of the above-mentioned The fourth step of obtaining the axis deviation between the cores of the pair of optical fibers from the eccentricity of the cores measured in the third step, and the axis deviation and the fourth step obtained in the second step.
A fifth step of obtaining the virtual positional deviation in the case where the axial deviation obtained in the step is the best match, and the virtual positional deviation obtained in the fifth step is estimated as the actual positional deviation between the optical connectors. It is characterized by doing.

In the fifth step, the virtual positional deviation is obtained when the sum of squares of the difference between the axial deviation obtained in the second step and the axial deviation obtained in the fourth step is the minimum. Is characterized by.

Further, the virtual positional deviation may be calculated when the sum of absolute values of the difference between the axial deviation obtained in the second step and the axial deviation obtained in the fourth step is the minimum.

In the case where optical connectors having guide pin holes into which positioning guide pins are inserted are formed on the coupling end surfaces, the guide pin holes of one of the optical connectors and the guide pin holes of the other optical connector are joined together. It is preferable that the positional deviation of (1) is the positional deviation between the optical connectors.

The invention according to claim 5 is a method for inspecting guide pin hole characteristics, which is obtained by temporarily fixing an optical fiber to an optical connector to be inspected and then performing the above-mentioned position deviation estimating method. The characteristic of the guide pin hole is inspected from the misalignment.

[0019]

According to the structure of the present invention, the relative positional deviation between the optical connectors can be obtained from the actual connection loss value and the measured value of the core eccentricity. That is, when the actual core axis deviation obtained from the connection loss value and the virtual positional deviation between the optical connectors and the virtual core axis deviation obtained from the measured value of core eccentricity are the best match, the virtual position at that time The deviation can be considered as an actual positional deviation. Therefore, by obtaining the connection loss value and the core eccentricity measurement value, it becomes possible to quantitatively evaluate the relative positional deviation between the optical connectors.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an optical connector to which the present invention can be applied, and FIGS. 1 (a) and 1 (b) are perspective views showing different viewing directions. Each of the optical connectors 1 and 2 has two guide pin holes 5a and 5b; 6a and 6b extending in parallel with each other on both sides of the front end faces (coupling end faces) 3 and 4, respectively. Also, these guide pin holes 5a, 5b;
A plurality of (16 in the illustrated embodiment) fiber holes are formed between 6a and 6b. The optical fibers 7 and 8 are inserted into the respective fiber holes, and the end faces of the optical fibers 7 and 8 are exposed from the openings of the fiber holes at the front end faces 3 and 4 of the optical connectors 1 and 2.

When such optical connectors 1 and 2 are coupled to each other, the front end faces 3 and 4 are made to face each other, and the guide pin holes 5a and 6a and the guide pin holes 5b and 6b which face each other are respectively guided by the guide pins 9a. , 9b are inserted for positioning, and the front end faces 3, 4 are butted against each other.

In the following description, one optical connector 1 is referred to as a sample side optical connector 1 and the other optical connector 2 is referred to as a master side optical connector 2 for distinction. Further, the relative positional deviation between the optical connectors 1 and 2 estimated according to the present invention is determined by the one guide pin hole 5 of the sample side optical connector 1.
Although it can be expressed as an axis deviation of the corresponding guide pin hole 6a of the master side optical connector 2 with respect to a, this axis deviation is further described in the following description in order to clarify the magnitude and directionality of the deviation. The rectangular coordinate system (XY coordinate system) defined with the guide pin hole 5a of the optical connector 1 as the reference is compared with the rectangular coordinate system (X'Y 'coordinate system) defined with the guide pin hole 6a of the master side optical connector 2 as the reference. It shall be expressed as a deviation.

When carrying out the method of the present invention, first, the pair of optical connectors 1 and 2 are connected to the guide pins 9a and 9 as described above.
The connection loss value between the optical fibers 7 and 8 of each pair that are abutted and coupled with each other through b is measured.

As described above, there is a correlation between the connection loss value and the core axis deviation, and the following equation is derived from equation (1).

[0026]

[Equation 2]

In the equation, i represents the i-th optical fiber from the reference guide pin hole 5a of the sample side optical connector 1, and Δ _oi
Is the core axis shift between the i-th optical fibers 7 and 8, and α _i is i
It is a connection loss value between the optical fibers 7 and 8 of the second pair.

Then, the cores of the optical fibers 7 and 8 in the optical connectors 1 and 2 are measured by an appropriate measuring method as described in Japanese Patent Application No. 4-226064 filed by the applicant of the present application. Measure the actual eccentricity.

An example in which the measuring method described in Japanese Patent Application No. 4-226064 is applied to the sample side optical connector 1 will be briefly described. In this measuring method, first, the illumination light is incident on the guide pin holes 5a and 5b from the rear end face 10 side, and the transmitted illumination light is imaged on the front end face 3 side to determine the center positions of the guide pin holes 5a and 5b. Ask. Next, based on the center positions of the guide pin holes 5a and 5b and the design data, the optical fiber 7 inserted into the fiber hole
Find the design position of the core center of. Then, the illumination light is incident on the optical fiber 7 inserted into the fiber hole from the rear end, and the emitted illumination light from the optical fiber 7 is imaged on the front end face 3 side to obtain the center position of the core of the optical fiber 7. . Thereby, the eccentricity of the center position of the core of the optical fiber 7 from the design position is measured. Master side optical connector 2
In the case of, the core eccentricity measurement value can be similarly obtained.

Now, the core eccentricity measurement value of each optical fiber 7 of the sample side optical connector 1 thus obtained is
The deviations x _si and y _si in the X and Y directions with reference to the coordinate system on the sample side optical connector 1 will be used. Further, the core eccentricity measurement value of each optical fiber 8 of the master side optical connector 2 is similarly expressed as displacements x _mi and y _mi in the X and Y directions with reference to the coordinate system on the sample side optical connector 1.

By the way, when the coordinate systems on the sample side optical connector 1 and the master side optical connector 2 coincide with each other, the two optical connectors 1 and 2 are accurately aligned by the guide pins 9a and 9b. However, in reality, a large number of positional deviations occur between the optical connectors 1 and 2.

Therefore, according to the present invention, it is assumed that there is a slight displacement between the coupled optical connectors 1 and 2. That is, as shown in FIG. 2, the coordinate system on the master side optical connector 2 is displaced from the coordinate system on the sample side optical connector 1 in the X direction by p, in the Y direction by q, and in the rotational direction by θ. Is caused.

In this way, the virtual positional deviation is set between the optical connectors 1 and 2, and the distance between the center of the reference Gund pin hole 5a and the core center of the designed i-th optical fiber 7 is d. _Assuming that _i is a very small value, the virtual core axis deviation Δ _i between the i-th optical fibers 7 and 8 is Δ _i.
Is calculated by the following equation.

[0034]

[Equation 3]

In the above equation, Δ _xi indicates the X-direction axial deviation between the i-th optical fibers 7 and 8, and Δ _yi indicates the Y-direction axial deviation between the i-th optical fibers 7 and 8. .

When this virtual core axis deviation Δ _i and the core axis deviation Δ _oi obtained from the measured connection loss value are the best match, the virtual position deviation at that time reproduces the actual position deviation. You are doing it.

When the core axis deviations Δ _i and Δ _oi are the best, they can be searched by using the least squares method. The least-squares method is an optimal solution (p, q, which minimizes the sum of squares of the differences between core axis deviations Δ _i and Δ _oi , as shown in the following equation.
θ) is obtained.

[0038]

[Equation 4]

The optimum solution in the above equation (4) can be obtained by using a search method generally called a hill climbing method. This hill climbing method can be applied to a microcomputer, and its processing procedure is as shown in the flowchart of FIG. Hereinafter, the optimum solution of the equation (4) is obtained according to this flowchart.

First, in step, initial values p ₀ , q ₀ and θ ₀ of p, q and θ are set.

Next, in the step, the initial values p ₀ , q ₀ , θ _{0 are} substituted into the formulas obtained by differentiating the above formula (4) by p, q, θ, and the calculation is performed. here,

[0042]

[Equation 5]

It is

After this, it is judged whether or not the absolute value of the value calculated in the step is sufficiently smaller than 1 (step).
The values of q and θ are slightly changed. Then, returning to the step, each new numerical value is substituted into the equations (5), (6) and (7).

The above steps, steps and steps are repeated, and when it is judged that the absolute value of the value calculated in the step is sufficiently smaller than 1, the step is moved to, and p, q, and θ at that time are changed. Output the value. These are the optimum solutions to be obtained, and the virtual deviation state of the coordinate system of the sample side optical connector 1 and the master side optical connector 2 in this solution can be considered as the actual positional deviation between the optical connectors 1 and 2.

FIG. 4 is a graph showing the results of actually carrying out the estimation method according to the present invention, and FIGS. 4 (a) and 4 (b).
Shows the connection loss value of each core at the first and second times when the same optical connector is attached and detached twice respectively. The solid line data shows the connection loss value obtained by actual measurement, and the dotted line data shows the calculated connection loss value in the position shift state obtained by the present invention. Comparing (a) and (b) in FIG. 4, the actually measured connection loss values are changing and the attachment / detachment fluctuations occur. It can be seen that the misalignment can be reproduced. Such a phenomenon of connection loss variation due to connector attachment / detachment cannot be quantitatively explained in the past.

In the above embodiment, 16 optical fibers 7 and 8 are used.
Regarding the optical connectors 1 and 2 connected to, the present invention can be applied as long as it is a multi-fiber optical connector having two or more fibers. Further, in the above embodiment, the hill-climbing method is used to solve the equation (4), but it is also possible to solve it by other methods. Further, in the above embodiment, the core axis deviation Δ
_Although the virtual axis deviation is calculated when the sum of squares of the difference between _i and Δ _oi is minimized, the sum of absolute values may be minimized instead of the sum of squares.

The method of estimating the positional deviation between the coupling connectors according to the present invention can also be applied to inspect the characteristics of the gund pin hole of the optical connector. That is, by temporarily fixing the optical fiber to the optical connector and applying the above method in that state to obtain the positional deviation between the connectors at the time of coupling, that is, the axial deviation of the Gund pin hole, the Gund pin hole characteristic can be inspected. . This makes it possible to improve the quality of the optical connector.

[0049]

As described above, according to the present invention, a positional deviation between optical connectors at the time of coupling or an axial deviation (guide pin hole characteristic) between gund pin holes, which could not be obtained in the past, is connected. It was possible to estimate from the loss value, which enabled quantitative evaluation. This is especially effective for analysis of attachment / detachment loss fluctuation, which is an important issue in quality assurance of optical connectors. Furthermore, by analyzing phenomenon of attachment / detachment loss fluctuation, appropriate measures for quality improvement are taken. be able to.

[Brief description of drawings]

FIG. 1 is a perspective view before connection showing a pair of optical connectors to which the present invention can be applied, where (a) is a view seen from a master side optical connector side, and (b) is a sample side optical connector side. It is the figure seen from.

FIG. 2 is a diagram showing a positional relationship between a rectangular coordinate system on a sample side optical connector and a rectangular coordinate system on a master side optical connector.

FIG. 3 is a flowchart for executing a hill-climbing method for obtaining an optimum solution when the sum of squares of the difference between the actual core axis deviation and the virtual core axis deviation is the smallest.

FIG. 4 is a graph showing the results of carrying out the estimation method according to the present invention, and (a) and (b) are respectively the first and second hearts when the same optical connector is attached and detached twice. It is a graph which shows the connection loss value of.

[Explanation of symbols]

1 ... Sample side optical connector, 2 ... Master side optical connector,
3, 4 ... Front end face (joint end face), 5a, 5b, 6a, 6b
... guide pin holes, 7, 8 ... optical fibers, 9a, 9b ... guide pins, 10 ... rear end face.

Claims (5)

[Claims] 1. A method of estimating a relative positional deviation between optical connectors when optical connectors having a plurality of optical fibers attached to each other are coupled to each other. The first step of obtaining the splice loss value between the two, the second step of obtaining the axial deviation between the cores of the optical fibers of each pair from the splice loss value, and the eccentricity of the core of each optical fiber in each optical connector are measured. In the third step, the position of the other optical connector is virtually displaced with respect to the one optical connector, and the axial deviation between the cores of the optical fibers of each pair at that time is measured by the third step. The fourth step obtained from the eccentricity, and the virtual position shift when the axial shift obtained in the second step and the axial shift obtained in the fourth step best match And a fifth step of obtaining a positional deviation estimation method between an optical connector and estimating a positional deviation between the actual optical connector the virtual positional deviation obtained in said fifth step. 2. The virtual positional deviation is calculated when the sum of squares of the difference between the axial deviation obtained in the second step and the axial deviation obtained in the fourth step is minimized. The method for estimating the positional deviation between the optical connectors according to claim 1, wherein 3. The virtual position deviation is obtained when the sum of absolute values of the difference between the axis deviation obtained in the second step and the axis deviation obtained in the fourth step is minimized. The method for estimating the positional deviation between the optical connectors according to claim 1. 4. A guide pin for one optical connector and a guide pin for the other optical connector when joining optical connectors having guide pin holes into which positioning guide pins are inserted in their coupling end faces. The positional deviation estimation method between optical connectors according to any one of claims 1 to 3, wherein the positional deviation of the holes is a positional deviation between the optical connectors. 5. An inspection method for inspecting the characteristics of a guide pin hole of an optical connector, according to claim 1, after temporarily fixing a plurality of optical fibers to the optical connector to be inspected. By estimating the positional deviation between the optical connectors by performing the positional deviation estimation method between the optical connectors of
A method for inspecting guide pin hole characteristics of an optical connector, which comprises inspecting the characteristics of a guide pin hole.