JP2716603B2 - Inspection method and apparatus for return loss of optical connector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical connector return loss inspection method and apparatus for inspecting the return loss of an optical connector used for connection between optical fibers in optical communication.

[0002]

2. Description of the Related Art With the advancement of optical communication and the increase in capacity, it is important to reduce the reflection of light at a connection point of an optical connector on a transmission line to a certain value or less in order to prevent deterioration of transmission quality. . That is, before providing the optical connector to the transmission line,
It becomes necessary to measure and inspect the return loss so as to meet the standard. Since a small reflection is equivalent to a large return loss, the return loss is hereinafter used as a measure of reflection.

FIG. 8 shows a method of measuring the return loss of an optical connector, which is widely used in the related art. In the figure, 11 is a light source for supplying measurement light, 12 is a light intensity detector for measuring reflected light intensity, 13 is an optical branching coupler for guiding reflected light to the light intensity detector, and 21 is one end. Total reflection coating 2
A total reflection reference optical code provided with 1a, 22 is a master optical code, 5 is an adapter for connecting optical connectors,
3 is an optical cord to be measured having an optical connector at both ends, 4 is an optical cord to be measured having an optical connector at one end, 23 is a refractive index matching agent for refractive index matching having the same refractive index as the optical fiber core, 3a, 4a and 22a are optical connectors. In the measurement, first, a light source such as an LD and a light intensity detector 12 for measuring reflected return light are connected to each branch end of the optical branching coupler 13. A light intensity detector when the total reflection reference optical code 21 is connected to the other end of the branch coupler 13
It is assumed that the reflected light intensity detected by No. 12 is P6 watt. next,
The master optical code 22 is connected to the branch coupler 13 in place of the total reflection reference optical code 21, and
The optical connector 22a is connected to the optical connector 3a or 4a of the optical cord 3 or 4 to be measured via the adapter 5, and the refractive index matching agent 23 is applied to the open end of the optical cord 3 or 4 to be measured. Let the reflected light intensity be P7 watts. The return loss Lr [dB] is calculated as P6, P
Based on the optical power of 7 watts, it is expressed as Lr = −10 log P7 / P6. Therefore, if the standard value of the return loss of the measured optical code 3 or 4 is Lrs [dB], the measured optical code satisfying Lr ≧ Lrs is a non-defective product.

[0004]

The reflection at the connection point of the optical connector occurs because a damaged layer having a different refractive index from that of the fiber core remains on the fiber end face due to polishing at the time of trimming. It is described that the return loss at the connection point of the optical connector can be described by the refractive index and the thickness of the processed deteriorated layer.
79, as revealed in the report. The problem in the conventional embodiment is that the state of the processing layer of the optical connector 22a of the master optical cord 22 is not specified at all. Hereinafter, problems of the conventional embodiment will be described with reference to FIGS.

First, FIG. 9 shows the return loss measured by the method shown in FIG. 8 using two types of master optical codes (low-reflection master optical code and high-reflection master optical code) having different processing layer states of the connector 22a. The cumulative probability density of the distribution. In the figure, the difference between the low-reflection master optical code and the high-reflection master optical code is that the low-reflection master optical code has a refractive index of a processed layer of the optical connector 22a relatively closer to the fiber core, or has a deteriorated layer. This is a point where the thickness is thin. The two curves in the figure are originally provided by the same optical code (s) to be measured, and the distribution by random connection of the optical codes to be measured is the same. From this figure, it can be seen that the measured return loss distribution differs depending on the master optical code. When a low-reflection master optical code is used, the return loss is relatively high, resulting in overestimation. In the case of a high-reflection master, the reverse is underestimated. An adverse effect due to the difference in the optical connector 22a of the master optical code occurs when an optical connector having a certain standard value or more is selected. For example, when an optical connector having a reflection standard value of 45 dB or more at the connection point is required due to the specifications of the optical transmission line or the like, 90% or more is a pass product in the measurement using the low reflection master optical code in FIG. However, only 10% of the high-reflection master optical codes are acceptable products, and there is a great difference in the yield despite the same optical code to be measured.

A further problem is that the return loss at the connector connection point when the optical cords to be measured that are selected so as to have a return loss equal to or greater than the standard value in the measurement according to the conventional example are connected at random. Is higher than the standard value. This will be described with reference to FIG. The figure shows the reflection per one connection point of the optical connector when the measured optical code of 45 dB or more is selected by using the low-reflection master optical code exemplified above as the master optical code 22 and the selected code is randomly connected. The cumulative probability density of the attenuation distribution is shown. As is apparent from FIG. 10, when the selection is performed by the low-reflection master optical connector, if the selection code is randomly connected through the transmission line, the number of connectors below the standard is 20%.
%. In such a case, transmission quality itself may be adversely affected.

As described above, in the conventional example, accurate measurement cannot be performed because the return loss distribution differs depending on the master optical code, the yield at the time of selection greatly changes, and the standard value is determined when the selected codes are connected at random. There are problems such as the following reflections. As a result, since the return loss of the optical code to be measured depends on the master optical code, highly reliable measurement and selection cannot be achieved.

[0008] The present invention has been made in view of the above,
It is an object of the present invention to provide an accurate and reliable method and apparatus for inspecting the return loss of an optical connector.

[0009]

In order to achieve the above object, a method for inspecting the return loss of an optical connector according to the present invention is provided in which an end face of an optical fiber is attached to a flat or convex spherical surface. Inspection of the return loss of the optical connector for determining whether the return loss of the optical connector that optically connects the pair of optical fibers that have been polished and trimmed is equal to or greater than a predetermined standard value Lrs [dB]. A method comprising: (a) a pair of measurement reference optical codes A and B having an optical connector polished to a flat or convex spherical surface on one end face; in connecting, the light intensity P ₀ watt measurement light incident to measure P ₁ watts reflected light intensity at the connection point, a step of determining the M from the following _{equation, -10log P 1 / P 0 =} Lrs + M ( Formula 1) (b) M and the above Return loss optical connector Lrs
(C) determining the constant N from the probability exceeding [dB]; and (c) the optical connector polished to the flat or convex spherical shape of the measurement reference optical code A and the flat or convex spherical shape at one end. Connecting the optical connector polished to the flat or convex spherical shape of the optical cord to be measured having the polished optical connector, and measuring the reflected light intensity P ₂ watt at the connection point; and And a step of determining whether or not the following equation is satisfied; and -10 log P ₂ / P ₀ ≧ Lrs + N (Equation 2).

The present invention also provides a device for inspecting the return loss of an optical connector, comprising a pair of trimmed optical fibers which are attached to the ends of the optical fibers and whose end faces are polished into flat or convex spherical surfaces. A return loss inspection device for the optical connector, which determines whether the return loss of the optical connector that optically connects the optical connector is equal to or greater than a predetermined standard value Lrs [dB].

A light source for supplying the measuring light, a light intensity detector for measuring the intensity of the reflected light from the object to be measured, and the reflected light from the object to be measured guided to the light intensity detector Connecting a pair of optical connectors polished to a flat or convex surface of each of a pair of measurement reference optical cords having an optical connector polished to a flat or convex spherical surface at one end face, and When the measuring light of P0 watts is incident and the reflected light intensity P1 watt at the connection point is measured, the value of M is stored from the formula of -10 log P1 / P0 = Lrs + M, and the value of M and the optical connector a calculation unit for return loss calculates the value of probability values or al N exceeding Lrs [dB], the value of the obtained N Tadashi
It corresponds to the left side of the above (Equation 2) rather than the sum of the case values Lrs
Return loss or reflection corresponding to the left side of (Equation 3)
When the amount of attenuation is large, the optical connector has a determination unit that determines that the optical connector is non-defective .

[0012]

In the inspection method of the reflection attenuation amount of the optical connector of the present invention, the measuring light intensity P _0, measuring the reference light code A, the optical connector connection points reflected light intensity P ₁ and standard measurement reference beam code B M is obtained from the relationship of the value Lrs [dB], and therefore, the state of the work-affected layer of the connector on the side of the measurement reference optical codes A and B connected to the measured optical code is indirectly obtained. Further, M and the return loss of the optical connector are Lrs
The constant N is determined from the probability of more than [dB], were selected measured light code from the light intensity P ₂ of first connection point of one end optical connectors with the measured light cord and the measurement reference beam code A in (Equation 2) ing. That is, the optical code to be measured that shows a higher return loss by N or more is selected for the reference optical code for measurement A in which the state of the processed deteriorated layer is indirectly obtained.
As a result, the connector at the end of the optical cord to be measured after the selection has a processed and deteriorated layer of a certain level or more. Therefore,
When the optical cables to be measured after selection are randomly connected, the return loss calculated per connection point of the connector is the standard value Lrs.
[DB].

Further, in the inspection apparatus for the return loss of the optical connector according to the present invention, the return loss inspection apparatus for the optical connector measures the light source for supplying the measurement light and the reflection light of the measurement light from the object to be measured. And a means for guiding the reflected light from the object to be measured to the light intensity detector. The light intensity detector detects the reflected light intensity at the connection point of the pair of measurement reference optical codes (formula 1). And a calculating unit for calculating the value of N from the value of M and the probability that the return loss of the optical connector of the optical code under test exceeds Lrs [dB], and the obtained value of N And a determination unit for determining the quality of the optical connector. Therefore, the return loss of the optical connector can be easily measured and selected.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of a method for measuring the return loss of an optical connector according to the present invention will be described with reference to FIGS. FIG. 1 is a connection diagram illustrating one embodiment of a method for measuring return loss of an optical connector according to the present invention, and FIG. 2 is a double-ended optical connector selected by one embodiment of the method for measuring return loss of an optical connector according to the present invention. This is the cumulative probability density of the return loss converted per connection point between the optical code to be measured and the optical code to be measured before being sorted. FIG. 3 shows the cumulative probability density of the return loss per connection point of the measured optical cord with one end optical connector selected by one embodiment of the method for measuring the return loss of the optical connector according to the present invention. In FIG. 1, reference numeral 1 denotes a reference optical code for measurement A, reference numeral 2 denotes a reference optical code for measurement B, reference numeral 3 denotes an optical code to be measured with a connector at both ends, reference numeral 4 denotes an optical code to be measured with a single-end connector, and reference numeral 5 denotes an optical connector. The adapters 1a, 2a, 3a, 3a ', and 4a are optical connectors whose optical fiber end faces are polished into a flat or convex spherical shape, and the adjusted end faces of the optical connectors 1b, 2b, and 13b are inclined with respect to the optical axis propagating through the optical fiber. Obliquely polished optical connector, 11 is a light source for supplying measurement light, 12 is a light intensity detector for measuring reflected light intensity, 13 is an optical branching coupler for guiding reflected light to the light intensity detector, 23 Is a refractive index matching agent for refractive index matching having the same refractive index as the optical fiber core.

First, a method for measuring the return loss of an optical connector according to the present embodiment will be described with reference to FIG. In this embodiment, the return loss standard value Lrs of the measured optical code is set to 45 [d
B], the refractive index n ₁ of the fiber core is 1.452, and the refractive index n _{2 of} air is 1.0. In the measurement, first, the light intensity detector 1 is connected to each branch end of the optical branching coupler 13.
2 is connected. Next, a method of defining the reference optical connectors A1 and B2 will be described with reference to FIG.

The obliquely polished optical connector 1 b of the reference optical code for measurement A 1 is connected to the obliquely polished connector 1 of the optical branching coupler 13.
3b, and an optical connector 1 of a reference optical cord A1 for measurement.
The intensity of reflected light returns to the optical intensity detector from the optical branching coupler 21 when the open end of a and P ₈ watts.

In the state of the above, the reference light code for measurement A1
The optical connector 2a of the reference optical cord for measurement B2 is connected to the optical connector 1a of the above through an adapter 5, and the reflected light intensity when the obliquely polished connector 2b of the reference optical cord for measurement B2 is open end is P ₁ watt. I do.

The measuring light P ₀ is expressed as follows using P ₈ , n ₁ and n ₂ .

-10 log 1 / P ₀ = -10 log 1 / P ₈
−20 log (n ₁ −n ₂ ) / (n ₁ + n ₂ ) The second term on the right side of the above equation corresponds to the Fresnel reflection of the fiber core and air, and is 14.7 [dB]. Therefore, M can be obtained as follows by modifying (Equation 1).

−10 log P ₁ / P ₈ + 14.7−45 = M (Equation 1 ′) The value of M generally indicates that the return loss distribution per connection point of the optical connector is approximately 40 to 60 [dB]. And the average value is 45 to 50 [dB], so that any optical connector can be used as the reference optical code for measurement.
It is assumed that 10 ≦ M ≦ 10 [dB].

Next, from the value of M and the probability that the return loss at the connection point exceeds the standard value Lrs [dB] even if the optical connector of the measured connector that has passed the inspection is randomly connected, the constant N Ask for. However, here, it is easier to proceed with the description of the embodiment after defining the inspection method. Therefore, it is assumed that the value of N is obtained for convenience. A detailed method of obtaining the value of N will be described later.

FIG. 1 shows a procedure for measuring the return loss of the optical code under test 3 with a double-ended connector and the optical code under test 4 with a single-ended connector using the standard optical code for measurement A1 and the standard optical code B2 for measurement. The description will be made according to the numbers and the numbers.

In the state of the above, the measurement reference optical code A1
Optical connector 1a and the optical connector 3a of the optical cord 3 to be measured.
When the optical connector 3a 'of the measured optical code 3 and the optical connector 2a of the measuring reference optical code B2 are connected via the adapter 5, respectively, and the obliquely polished connector 2b of the measuring reference optical code B2 is set to the open end. The reflected light intensity of P ₂ + P ₃
Watts.

In the state of the above, the reference light code for measurement A1
Of the optical connector 1a of the measured light cord 4 optical connector 4 a
Is connected via an adapter 5 and the reflected light intensity when the refractive index matching agent 23 is applied to the fiber end face at the other end of the optical cord 4 to be measured is P2 watts.

The return loss of the measured optical cord 3 with connectors at both ends is represented by the left side of the following equation, and the standard value Lrs = 4
If the value is equal to or higher than N [dB] than 5 [dB], it is regarded as a good product.

−10 log (P ₂ + P ₃ ) / P ₈ + 14.7 ≧ 45 + N (Equation 2 ′) On the other hand, the return loss of the measured optical cord 4 with one end connector is represented by the left side of the following equation. Value Lrs = 45 [d
If it is equal to or more than N [dB] higher than B], it is regarded as good.

−10 log P ₂ / P ₈ + 14.7 ≧ 45 + N (Equation 3 ′) If the light intensity detector has a function of correcting the display value of the light intensity, the reference light code A for measurement is obtained by the following method.
After determining 1, 1 and B2, the display value of the light intensity detector in the connection state is corrected to 14.7 [dB], or the power meter display value in the connection state is (Equation 2 ') or (Equation 2'). As the left side of 3 ′), the measured optical codes 3 and 4 may be selected by comparing with the values on the right side.

In the following, it is assumed that if the measured optical cords 3 or 4 are randomly connected and the return loss at the connection point of the connector 1 exceeds the standard value with a probability of 99% or more, the object of the selection is reached. Determine the value of M to N. In FIG.
Assuming that M = 5 [dB] and N = 0 [dB] in the above measurement method, when the measured optical cords 3 with double-ended connectors selected in (Equation 2 ′) are randomly connected, the connection point of the connector 1 is determined. 6 shows a cumulative probability density distribution of return loss. The optical cord 3 to be measured in this embodiment is the same as that used in the conventional example described with reference to FIG.

FIG. 2 also shows the return loss distribution converted per connection point when the optical cords 1 to be measured before selection are randomly connected. As shown in FIG. 2, before the selection, the probability that the return loss is less than or equal to the standard value Lrs = 45 [dB] is about 30%, whereas M = 5 in the measurement in this embodiment.
After selecting as [dB], N = 0 [dB], 99%
With the above probability, the value exceeds the standard value.

On the other hand, FIG. 3 shows that M = 5 [d
B], N = 2 [dB], and the cumulative probability density distribution of the return loss at the connection point of the connector 1 when the measured optical cord 4 with one end connector selected in (Equation 3 ′) is connected at random. Show. As in the case of the cord under test 3 with connectors at both ends, after selection with M = 5 [dB] and N = 2 [dB], the value becomes the standard value or more with a probability of 99% or more.

The effect of this embodiment is apparent from comparison with FIG.

As described above, the return loss inspection method for the optical connector according to the present embodiment has the following features.

The first point is that an optical code to be measured that shows a return loss equal to or more than a predetermined reference with respect to the reference optical codes A and B for measurement in which the affected layer is defined is selected. The connector of the optical cable under test after sorting is
It will have a work-affected layer of a certain level or more. Therefore, if the optical cables to be measured after selection are connected at random,
The return loss calculated per connection point of the optical connector exceeds the standard value Lrs [dB] with a high probability.

The second point is that the connector of the optical branching coupler, the connector on the optical branching coupler side of the measuring reference optical code A, and the connector on the open end side of the measuring reference optical code B are obliquely polished connectors. This has the effect of suppressing the reflected light from points other than the connector connection point between the optical cord to be measured and the measurement reference optical cord, and as a result, highly accurate measurement is possible.

The third point is that since the measurement is based on the Fresnel reflection of air and the fiber core as a reference, the optical code to be measured can be continuously measured and selected without replacing the reference optical code A for measurement. A difference in return loss due to a connection loss between the reference optical code A for use and the optical branching / coupling device can be avoided, and accurate measurement can be performed.

The fourth point is that the measurement reference optical code A
If only B1 and B2 are prepared, the return loss when the optical cord to be measured is connected can be measured, and the quality of the optical cord to be measured can be determined based on whether or not the measured value is equal to or greater than the standard value.
Excellent economy.

The fifth point is that the range of the value of M is -10 ≦
Since M ≦ 10 [dB], any optical connector can be used as the reference optical code for measurement, so that the reference optical code for measurement can be easily determined.

In this embodiment, the relationship between the reference optical code A1 for measurement and the reference optical code B2 for measurement may be reversed, and the optical connectors 3a and 3a 'of the optical cord 3 to be measured with connectors on both ends are required. It goes without saying that the connection may be reversed with respect to the measurement reference optical code A1 and the measurement reference optical code B2.

A second embodiment of the method for testing return loss of an optical connector according to the present invention will be described with reference to FIG. FIG. 4 shows a return loss standard value with a probability of 99% for the return loss per connection point when a good optical cable under test is randomly connected in the return loss measurement method for an optical connector according to the present invention. FIG. 9 is a diagram illustrating the relationship between M and N in (Equation 1) to (Equation 3) when Lrs [dB] is exceeded. In the figure, the plots are the simulation results, the plots represent the measured optical codes with optical connectors at both ends, the plots represent the measured codes with optical connectors at one end, and the straight lines represent the linear regression of the plots. From the regression line, N ≧ 0.4M−2.0 in the case of the measured optical code with the optical connector at both ends, and N ≧ 0.45M in the case of the measured code with the optical connector at one end.
If it is −0.3, the probability that the return loss per connection point exceeds the return loss standard value Lrs [dB] is 99% or more when non-defective optical cables under test are connected at random. Becomes Therefore, if the measurement is performed by setting the values of N and M in at least the shaded area in the figure where N ≧ 0.4M−2.0, the measured code with both ends and one end optical connector has a high probability. Return loss per connection point is the standard value Lrs
[DB]. The values of M and N in the first embodiment are both within the shaded area in FIG.

A third embodiment of the method for defining a reference optical code for measurement in the method for testing return loss of a high connector according to the present invention will be described with reference to FIGS. FIG. 5 is a connection diagram for explaining an embodiment for defining a reference optical code for measurement in the method for testing the return loss of an optical connector according to the present invention.
FIG. 4 is a diagram showing variations in N values according to the defined reference in an example in which a measurement reference optical code is defined. FIG.
, 1 is a reference optical code for measurement A, 2 is a reference optical code for measurement B, 4 is an optical code to be measured with a single-ended connector, 5
Are adapters for connecting optical connectors, 1a, 2a, 4
a is an optical connector in which the end face of an optical fiber is polished into a flat or convex spherical shape, 1b, 2b, and 13b are obliquely polished optical connectors in which the adjusted end face is inclined with respect to the optical axis propagating through the optical fiber, and 11 is a measuring light. 12 is a light intensity detector for measuring the reflected light intensity, 13 is an optical branching coupler for guiding the reflected light to the light intensity detector, and 23 has a refractive index equivalent to that of the optical fiber core. It is a refractive index matching agent for refractive index matching.

First, a method of defining the reference optical codes A1 and B2 for measuring the return loss of the optical connector according to the present embodiment is shown in FIG.
It will be described according to. First, the light intensity detector 12 is connected to each branch end of the optical branching coupler 13. Subsequently, the oblique polishing optical connector 1b of the measurement reference optical code A1
Is connected to the oblique polishing connector 13b of the optical branching coupler 13, and the optical branching coupler 13 to the light intensity detector 12 when the refractive index matching agent 23 is applied to the fiber end face of the optical connector 1a of the measuring reference optical code A1. the intensity of the reflected light coming back to the P ₄ watts.

The obliquely polished optical connector 2 b of the measurement reference optical code B 2 is connected to the obliquely polished connector 1 of the optical branching coupler 13.
3b and the optical connector 2 of the reference optical cord for measurement B2.
The intensity of reflected light returns to the optical intensity detector from the optical branching coupler 13 when applied a refractive index matching agent 23 to the fiber end face of a and P ₅ watts.

The obliquely polished optical connector 1 b of the measurement reference optical code A 1 is connected to the obliquely polished connector 1 of the optical branching coupler 13.
3b, and an optical connector 1 of a reference optical cord A1 for measurement.
The optical connector 4 a of the light to be measured code 4 is connected via the adapter 5 in a, by applying a refractive index matching agent 23 of the fiber end face of the other end of the measured optical code 4, as in the first embodiment In this case, the value of N exceeding the return loss standard value Lrs [dB] is NA [d
B].

The oblique polishing optical connector 2 b of the measurement reference optical code B 2 is connected to the oblique polishing connector 1 of the optical branching coupler 13.
3b and the optical connector 2 of the reference optical cord for measurement B2.
The optical connector 4 a of the light to be measured code 4 is connected via the adapter 5 in a, by applying a refractive index matching agent 23 to the fiber end face of the other end of the measured optical code 4, as in the first embodiment In this case, the value of N which exceeds the return loss standard value Lrs [dB] with a probability of 99% or more is NB [d
B].

In the reference optical cords for measurement A1 and B2, since there is a difference in processing deterioration between the end faces of the optical connectors 1a and 2a, when selecting the optical cord to be measured 4 with a single-end optical connector,
It is expected that N _A and N _B are different in. In order to perform highly reliable measurement and selection, it is necessary to minimize variations in N due to the reference optical code. Effectively, the variation of N is 1.0
[DB] or less is preferable. FIG. 6 shows -10 log P ₄
The absolute value of the / P _5, shows the relationship between the absolute value of the N _A -N _B representing the variation of the N values. In the figure, the plot is a simulation result, and the straight line represents a first-order regression of the plot. From the regression line, | N _A −N _B | ≦ 1.0 [dB] can be obtained by | -10 log P ₄ / P ₅ | ≦ 2.0 [dB] (Equation 4). The small variation in N means that the optical connectors 1a of the measurement reference optical codes A1 and B2 are indirectly connected.
And 2a mean that the deformation of the end face is the same. Therefore, if the reference optical code is defined so as to satisfy the condition of (Equation 4), the return loss of the measured optical code 4 with one end optical connector can be measured using either of the reference optical codes for measurement A1 and B2. With a stable probability, the optical connector after sorting becomes equal to or more than the reference value, and the measurement is highly reliable.

As described above, in the method for inspecting the return loss of the optical connector in this embodiment, the reference optical code A for measurement is used.
And B, since there is light that defines the processing-affected layer of the connector connected to the optical cord to be measured in substantially the same state, a highly reliable inspection can be performed.

A fourth embodiment of the optical connector return loss inspection apparatus according to the present invention will be described with reference to FIG. In the drawing, reference numeral 1 denotes a reference optical code for measurement A, reference numeral 2 denotes a reference optical code for measurement B, reference numeral 3 denotes a measurement optical code with connectors at both ends, 1a, 2a,
3a, 3a 'are optical connectors whose optical fiber end faces are polished into a flat or convex spherical shape, 1b, 2b, 13b are obliquely polished optical connectors whose adjusted end faces are oblique to the optical axis propagating through the optical fiber, 11 Is a light source for supplying measurement light,
Is a light intensity detector for measuring the reflected light intensity, 13 is an optical branching coupler for guiding the reflected light to the light intensity detector, 14 is a memory for storing the value of M, and the value of M and the reflection of the optical connector. A calculating unit for calculating the value of N from the probability value that the attenuation exceeds Lrs [dB]; and 15 determining whether or not the measured optical code is good based on the determined value of N and the reflection attenuation of the optical connector of the measured optical code. The determination units 30 and 31 are return loss inspection devices.

First, description will be made with reference to FIG. The return loss inspection device 30 is composed of devices within a chain line in the figure, that is, a light source 11, a light intensity detector 12 , an optical branching / coupling unit 13, an operation unit 14, and a determination unit 15. The measurement procedure and the result method of each code are the same as those in the first embodiment. However, the arithmetic unit 14 stores M obtained from the measurement reference optical codes A1 and B2, and outputs the light to be measured as shown in the second embodiment. The value of N is calculated from the probability value that the return loss of the optical connector of the code exceeds Lrs [dB].
It has a function of judging the quality of the measured optical code from the return loss of the measured optical code connected to the measuring reference optical code and N calculated by the arithmetic unit.

Therefore, the return loss inspection apparatus 30 can automatically calculate and determine even if an arbitrary optical code is selected as the reference optical code for measurement, so that the reference optical code for measurement can be easily selected and measured. Optical code inspection can be performed.

Next, FIG. 7B will be described. The return loss inspection device 31 includes devices within a chain line in the figure, that is, a light source 11, a light intensity detector 12, an optical branching coupler 13,
The determination unit 15 is composed of the reference optical codes for measurement A1, B2. The measurement procedure and the like are the same as those in the first embodiment, but since the reference optical codes for measurement A1 and B2 are incorporated in the apparatus in advance, M is known and N is uniquely determined.
Therefore, the calculation unit in the above-described inspection apparatus 30 becomes unnecessary, and the determination unit 15 can determine the quality of the measured optical code from the reflection attenuation amount and the N of the measured optical code connected to the measurement reference optical code. it can.

Therefore, the reflection-attenuation amount inspection apparatus 31 can be easily constructed, so that the optical code to be measured can be inspected at low cost, and the inspection can be easily performed because the reference optical code for measurement is already incorporated in the apparatus.

In this embodiment, the system for measuring the reflected light is constituted by a pulse light source and an optical switch.
It is needless to say that the same effect can be obtained even in the case of the R type or the interferometric OTDR type including an interferometer.

[0054]

As described above, the method for inspecting the reflectivity of an optical connector according to the present invention can perform a highly reliable inspection and, when the optical cords to be measured after the selection are randomly connected, are connected to one connection point of the optical connector. The return loss converted per unit exceeds the standard value with a high probability, and an inspection with high accuracy can be performed. Further, it is possible to easily provide a highly reliable and easily operable return loss inspection apparatus. Therefore, an optical connector having a return loss per connection point equal to or larger than the standard value can be provided simply and reliably, and as a result, the effect of configuring a high-quality optical fiber transmission line is great.

[Brief description of the drawings]

FIG. 1 is a connection diagram illustrating a configuration of an embodiment of a method for inspecting a return loss of an optical connector according to the present invention.

FIG. 2 is a diagram showing the relationship between the return loss and the cumulative probability density converted per connection point of a measured optical code with optical connectors at both ends selected according to the embodiment of FIG. It is.

FIG. 3 is a diagram showing the relationship between the return loss converted per connection point of the optical code to be measured with the one-end optical connector selected according to the embodiment of FIG. 1 and the optical code to be measured before the selection and the cumulative probability density; It is.

FIG. 4 is a standard of the return loss with a probability that the return loss per connection point is 99% when random optical cables to be measured are randomly connected in the return loss test method of the optical connector according to the present invention. It is a figure showing the relation of M and N when it exceeds a value.

FIG. 5 is a connection diagram showing the configuration of an embodiment for defining a reference optical code for measurement in the method for inspecting the return loss of an optical connector according to the present invention.

FIG. 6 is a diagram showing a variation in N value according to a prescribed reference in the embodiment of FIG. 5;

FIG. 7 is a diagram showing an embodiment of the inspection apparatus for the return loss of the optical connector according to the present invention.

FIG. 8 is a connection diagram showing a conventional method for inspecting the return loss of an optical connector.

FIG. 9 is a diagram showing the relationship between the return loss of a measured optical code and the cumulative probability density selected by the conventional method of checking the return loss of an optical connector.

FIG. 10 is a diagram showing the relationship between the return loss and the cumulative probability density per connection point of a connector of the optical cord to be measured, which is selected by the conventional method for checking the return loss of an optical connector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measurement reference optical code A 2 Measurement reference optical code B 3 Optical code to be measured with a connector at both ends 4 Optical code to be measured with a connector at one end 5 Adapter 1a, 2a, 3a, 3a'4a Optical connector 1b, 2b, 13b Oblique polishing Optical connector 11 Light source 12 Light intensity detector 13 Optical branching coupler 21 Total reflection reference optical code 21a Total reflection coating 22 Master optical code 23 Refractive index matching agent 30, 31 Return loss inspection device

Claims (7)

(57) [Claims] 1. An optical connector which is attached to an end of an optical fiber and polished the end face of the optical fiber into a flat surface or a convex spherical shape and optically connects a pair of optical fibers that have been trimmed, has a return loss. A method for inspecting the return loss of an optical connector for determining whether or not it is equal to or greater than a predetermined standard value Lrs [dB], comprising: (a) having an optical connector polished to a flat or convex spherical surface on one end face; connect the pair of measurement reference beam code a and B in the optical connector polished in each of the planar or convex spherical, the light intensity P ₀ watt measurement light incident reflected light intensity at the connection point P ₁ Measuring watts and determining M from the following equation: -10 log P ₁ / P ₀ = Lrs + M (Equation 1) (b) The return loss of the M and the optical connector is Lrs
(C) determining the constant N from the probability exceeding [dB]; and (c) the optical connector polished to the flat or convex spherical shape of the measurement reference optical code A and the flat or convex spherical shape at one end. Connecting the optical connector polished to the flat or convex spherical shape of the optical cord to be measured having the polished optical connector, and measuring the reflected light intensity P ₂ watt at the connection point; and Determining whether the following equation is satisfied: -10 log P ₂ / P ₀ ≧ Lrs + N (Equation 2) A method of inspecting the return loss of an optical connector. 2. In the step (c), the optical connector polished into the flat or convex spherical shape and the optical connector polished into a flat or convex spherical shape at both ends of the measurement reference optical code A are used. An optical connector polished to one plane or a convex spherical shape of the optical code to be measured is connected, and the optical connector polished to the flat or convex spherical shape of the measurement optical code B and the other of the optical code to be measured are connected. This is a step of connecting an optical connector polished into a flat or convex spherical shape and measuring the reflected light intensity P ₂ + P ₃ watts at the connection point. (Equation 2) in the step (d) is the following equation. . _{-10log (P 2 + P 3)} / P 0 ≧ Lrs + N ( Equation 3) inspection method of the reflection attenuation amount of the optical connector according to claim 1, wherein a. 3. The relationship between M and N is N ≧ 0.4M-2.
3. The method according to claim 1, wherein the return loss is zero. 4. The pair of measurement reference optical cords has an optical connector polished into a flat or convex spherical shape at one end, and connects the optical connector polished into a flat or convex spherical shape at each end. Then, a measuring light having a light intensity of P ₀ watts is incident,
When the reflected light intensity P ₁ watt at the connection point is measured, the range of the value of M obtained from the equation of −10 log P ₁ / P ₀ = Lrs + M is −10 ≦ M ≦ 10
4. The method according to claim 1, wherein the return loss is [dB]. 5. An optical connector polished to one of the pair of measurement reference optical cords having a flat or convex spherical shape coated with a refractive index matching agent having a refractive index equivalent to that of a fiber core and terminated. the reflected light intensity and P ₄ watts, P ₅ the reflected light intensity of the other a polished optical connector該整the mixture applied to the to the plane or convex spherical of the measurement reference beam code while terminating The return loss of the optical connector according to any one of claims 1 to 3, wherein the following expression is satisfied: | -10 log P ₄ / P ₅ | ≦ 2.0 (Equation 4). Inspection methods. 6. An optical connector which is attached to an end of an optical fiber and optically connects a pair of trimmed optical fibers whose end faces are polished into a flat or convex spherical shape, has a predetermined return loss coefficient. And an optical connector for measuring the return loss of the optical connector, which determines whether the measured value is equal to or more than the standard value Lrs [dB]. A light intensity detector for guiding a light reflection from the object to be measured to the light intensity detector, and a pair of measurement devices having an optical connector polished to a flat or convex spherical surface on one end surface. An optical connector polished to a flat or convex spherical shape of each reference optical cord is connected, a measuring light having a light intensity Po watt is incident, and a reflected light intensity P1 watt at the connection point is measured. / P0 = Lrs + M becomes stores the value of M from the equation, the value and the reflection attenuation amount of the optical connector of the M and a calculator for calculating the value of the probability value or al N exceeding Lrs [dB], the obtained N- Value and the standard value Lrs,
Return loss corresponding to the left side of (Equation 2) or the above (Equation 2)
(3) a device for determining the return loss of an optical connector , comprising: a determination unit for determining the optical connector as a non-defective product when the return loss corresponding to the left side is large . 7. The apparatus according to claim 6, wherein the value of M is determined in advance in accordance with the pair of measurement reference optical codes.