JP6439888B1 - Reflected light measuring device - Google Patents

Abstract

A reflected light measuring apparatus capable of efficiently performing a disconnection inspection on optical connectors at both ends and a plurality of optical fibers. A reflected light measuring apparatus includes a laser light source, a beam splitter that branches into a measuring laser beam that transmits the measuring laser beam and a reference laser beam that reflects, and an optical path length of the reference laser beam. A reference mirror 4 having a variable optical path length mechanism, and an optical path length switching unit 5 disposed between the reference mirror 4 and the beam splitter 3 for switching the optical path length of the reference laser beam L2 to a plurality of fixed lengths. The measurement laser beam L1 ′ reflected at the defective portions D1 and D2 such as the disconnection in the connectors to be measured C1 and C2 connected to the connection portion 7 and the reference laser beam L2 ′ reflected by the reference mirror 4 are passed through the beam splitter 3. And an optical measuring device 6 for receiving light. [Selection] Figure 1

Description

  The present invention relates to a reflected light measuring device for identifying a defective portion such as a crack or disconnection of a material to be measured made of a light-transmitting material such as an optical fiber, and measuring and digitizing reflected light generated at the defective portion. It is.

  Since optical fibers use glass as a main material, there is a problem that disconnection and cracks are likely to occur. In particular, when processing into the optical connector, stress is often applied to the optical fiber, and disconnection often occurs in the optical connector.

  In the state immediately after the occurrence of the disconnection in the optical connector, the optical fibers at the disconnection point are in close contact with each other, so that the amount of light is transmitted through the optical fiber with almost no change. Further, when the broken surface of the optical fiber has a mirror-like shape without streak-like irregularities, and the broken surface has a slope shape, the reflected light becomes very weak. In the case of a disconnection in which there is almost no reflected light due to such a disconnection point, that is, a so-called hidden disconnection, a problem hardly occurs at the beginning of use.

  However, when this hidden disconnection has passed for a long time, the optical fibers are gradually separated in the hidden disconnection due to repeated expansion and contraction accompanying the temperature change of the adhesive used in the optical connector and vibration applied to the optical connector. , The transmission performance of the optical fiber may be deteriorated, and communication failure or the like may occur.

  Therefore, immediately after the assembly of the optical fiber to the optical connector, a disconnection inspection using light reflection generated at the disconnection portion is performed. Patent Document 1 describes an optical fiber measuring device that measures the position and size of a defect in the entire length of an optical fiber using an optical interference method.

Japanese Patent Laid-Open No. 7-83790

  A manufacturer of an optical fiber cable that sells an optical fiber incorporated in an optical connector, for example, uses the measuring device disclosed in Patent Document 1 to inspect the disconnection state for each product and then ships only good products. And when a hidden disconnection is discovered after shipment, it is preferable that the manufacturer can prove to what level the reflected light accompanying the disconnection was inspected at the time of shipment.

  However, in the measurement apparatus described in Patent Document 1 described above, a rough disconnection state can be measured from the strength of reflected light from an optical fiber, but only weak reflected light such as a hidden disconnection can be obtained. Therefore, it is not possible to perform measurement with sufficient accuracy to present the reflected light at the disconnection point as a numerical value. Therefore, there is a problem that it is impossible to explain to the user the level of the reflected light that has been inspected at the time of shipment of the measuring apparatus.

  In addition, the disconnection inspection in the optical connector of the optical fiber cable is performed by connecting the optical connector to a measuring device, and the optical fiber cable has optical connectors at both ends. For this reason, when performing a disconnection inspection, after inspecting one optical connector, it is necessary to remove the one optical connector, connect the other optical connector, and inspect the other optical connector, and the measurement work is complicated. It took time and effort.

Furthermore, when disconnecting multiple optical fibers such as an optical fiber cable with an MPO (Multi-fiber Push-On) connector at one end, repeated connection work is required for each optical fiber. Therefore, the time required for the disconnection inspection becomes enormous.
Therefore, the manufacturer of the optical fiber obtained by quantifying how much reflected light was inspected with respect to the emitted light of the measuring device in a disconnected state, and tested it to a predetermined reflectivity that can be measured. An inspection device that can guarantee the quality is desired. In particular, for optical connectors attached to both ends of an optical fiber, and further to a plurality of optical connectors attached to a plurality of optical fibers, an inspection apparatus capable of measuring the reflectance in a short time and a simple operation is required. ing.

  An object of the present invention is to solve the above-mentioned problems, obtain the occurrence position of a defective portion such as a crack or disconnection in an optical connector, quantify reflected light with high reliability, An object of the present invention is to provide a reflected light measuring apparatus capable of efficiently performing a disconnection inspection on an optical fiber.

Reflected light measurement apparatus according to the present invention for achieving the above object, a laser light source for emitting a laser beam, a beam splitter for splitting the reference laser beam to measure the laser light and the reflected transmitted through the laser light, the beam Defective test object made of translucent material, connecting portion arranged on optical path of measurement laser light transmitted through splitter, reference mirror having optical path length variable mechanism capable of adjusting optical path length of reference laser light A light measuring device that receives the measurement laser light reflected at the location and the reference laser light reflected by the reference mirror via the beam splitter, and the reference laser light and the measurement received by the light measuring device. In the reflected light measuring apparatus for detecting the defective portion based on interference light from a laser beam, the beam splitter and the reference are used. Between the mirror, wherein the switching unit for switching the optical path of the reference laser beam is arranged.

  According to the reflected light measuring apparatus of the present invention, the position of a defective portion such as a disconnection or a crack in an optical connector in which the reflected light is extremely weak is detected, and the reflected light is to what level with respect to the emitted light. Can be converted into a numerical value and output.

  Further, it is possible to continuously inspect the optical connectors attached to both ends of the optical fiber without changing the connection state of the optical fiber to the reflected light measuring device. Similarly, it is possible to continuously inspect optical connectors such as MPO connectors and other translucent materials such as contact lenses and translucent materials using optical paths of measurement laser beams arranged in parallel. It is.

1 is a configuration diagram of a reflected light measurement device of Example 1. FIG. It is a flowchart figure which shows the disconnection failure detection method by the reflected light measuring apparatus of Example 1. FIG. It is a graph of the relationship between the distance of a defective part, and the reflection level of interference light. It is a block diagram of the reflected light measuring apparatus of Example 2. It is a block diagram for obtaining characteristic data of a reference optical attenuator using an optical measuring device. It is a graph figure of the characteristic data of an optical attenuator. It is a block diagram in the case of performing a reference setting process. It is a block diagram for obtaining a calibration line. It is a graph figure of the calibration line used with a reflected light measuring device.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a configuration diagram of a reflected light measuring apparatus 1 according to the first embodiment. The reflected light measuring apparatus 1 includes a connector to be measured and a connector to be measured of an optical fiber cable FC having measured connectors C1 and C2 at both ends. C1 is connected. The inspection of a defective portion such as a disconnection with respect to the connectors C1 and C2 to be measured by the reflected light measuring device 1 is based on the principle of a Michelson interferometer.

The reflected light measuring device 1 equally divides the amount of light into a laser light source 2 that emits laser light L, which is low interference light, and a measurement laser light L1 that transmits the measurement laser light L and a reflected reference laser light L2. And a reference mirror 4 having a variable optical path length mechanism capable of adjusting the optical path length of the reference laser beam L2, and an optical path length of the reference laser beam L2 disposed between the reference mirror 4 and the beam splitter 3. Is switched to a plurality of fixed lengths, the measurement laser beam L1 ′ reflected at the defective portions D1 and D2 such as disconnection in the connectors C1 and C2 to be measured, and the reference laser beam L2 ′ reflected by the reference mirror 4 Is composed of a light measuring device 6 that receives light through the beam splitter 3 and a connection portion 7 disposed on the optical path of the measurement laser light L1 that has passed through the beam splitter 3. It has been.
Further, in order to maintain the stability with respect to the temperature characteristics of the laser light, the laser light source 2 is temperature controlled by a Peltier element or the like.

  The reflected light measuring device 1 is connected to a calculation control unit (not shown). The calculation control unit controls the operation of each member, calculates the measurement value of the light measuring device 6 and the like. The position and the degree of are numerically output. In particular, the arithmetic control unit has a function of storing a calibration line, which will be described later, and calculating the reflectance based on the calibration line from the measurement value obtained by the optical measuring device 6.

  The measurement laser light L emitted from the laser light source 2 is branched by the beam splitter 3, and the measurement laser light L1 that has passed through the beam splitter 3 and traveled straight is transmitted to the connector C1 and the connector C2 to be measured. The optical path from the beam splitter 3 to the connector to be measured C1 and the connector to be measured C2 is an optical fiber, and the connectors to be measured C1 and C2 are connected via a connecting portion 7 provided at the end of the optical fiber.

  A part of the measurement laser light L is reflected by the beam splitter 3 to become the reference laser light L 2, and is transmitted to the optical path length switching unit 5. The optical path length switching unit 5 includes optical switches 50 at both ends, and a plurality of fixed-length optical fibers having predetermined optical path lengths are arranged in advance at connection terminals (not shown) of these optical switches 50.

  These fixed length optical fibers include a first fixed length optical fiber 51 having an optical path length for the connector to be measured C1 which is an optical connector at one end of the optical fiber cable FC, and a connector to be measured C2 which is an optical connector at the other end. The second fixed-length optical fiber 52 having an optical path length is connected to the optical switch 50 in parallel.

  Two or more second fixed-length optical fibers 52 may be arranged according to the length of the optical fiber cable FC, and the above-mentioned connection terminals are arranged on the outer surface of the reflected light measuring device 1 and the first fixed The long optical fiber 51 and the second fixed length optical fiber 52 may be appropriately exchanged according to the length of the optical fiber cable FC.

  In the configuration diagram of FIG. 1, a pair of optical switches 50 are arranged, but only one optical switch 50 near the beam splitter 3 may be arranged. In such a case, the optical path including the first fixed length optical fiber 51 and the optical path including the second fixed length optical fiber 52 to the reference mirror 4 are arranged in parallel, and for each optical path, It is possible to change the optical path length by an optical path length variable mechanism described later.

  By switching the optical switch 50, the reference laser light L2 passes through the first fixed-length optical fiber 51 or the second fixed-length optical fiber 52 and has a predetermined optical path length. At this time, the optical path length of the first fixed-length optical fiber 51 is set to be substantially equal to the optical path length to the connection portion 7 of the measurement laser light L1.

  On the other hand, the optical path length of the second fixed length optical fiber 52 is set substantially equal to the optical path length of the first fixed length optical fiber 51 plus the optical path length of the optical fiber cable FC to be inspected. The reference laser beam L2 branched by the beam splitter 3 in this way is transmitted to the reference mirror 4 through the optical path length switching unit 5. The reference mirror 4 includes an optical path length variable mechanism that can move to an arbitrary position along the optical axis of the reference laser beam L2, and fine adjustment is added to the optical path length of the reference laser beam L2.

  The optical path length variable mechanism of the reference mirror 4 can also use a rotating reflector. This rotary reflector employs a mechanism having a radius of 20 mm and a rotation speed of about 1.1 rotations / second in order to ensure a variable range of 20 mm as the measurement length.

  Further, if there is a defective part such as a disconnection in the connector to be measured C1 or C2, the measurement laser light L1 'reflected at the defective part D1 or D2 is reflected by the beam splitter 3 and transmitted to the optical measuring device 6.

  On the other hand, the reference laser beam L2 is transmitted by selectively switching the first fixed-length optical fiber 51 or the second fixed-length optical fiber 52 by the optical switch 50, reflected by the reference mirror 4, and the reference laser beam L2. Then, the first fixed-length optical fiber 51 or the second fixed-length optical fiber 52 is selectively switched by the optical switch 50 and transmitted, and transmitted through the beam splitter 3 and transmitted to the optical measuring device 6. The

  In addition, an optical fiber is used for each optical path, and the measurement laser light L can be made to travel straight and branch using a fiber coupler instead of the beam splitter 3. In addition, a lens optical system is used in the optical path of the actual interferometer, and further, a polarizing beam splitter and a quarter wavelength plate may be used. .

  The laser light source 2 emits, for example, a low-interference laser beam having a wavelength of 1310 mm, the defect measurement range near the optical fiber in the connectors C1 and C2 to be measured is, for example, 0 to 20 mm, and the measurement resolution length is, for example, 1.25 μm. Has been. For this reason, the variable range of the optical path length variable mechanism of the reference laser beam L2 is also equivalent to 20 mm. The optical path length variable range is substantially the same as the optical path length of the connectors C1 and C2 to be measured and should be changed according to the size of the connector, and is not limited to 20 mm.

  Next, a method of detecting the position of the defective optical connector by the reflected light measuring device 1 is shown in the flowchart of FIG. First, in step S101, the connector to be measured C1, which is an optical connector at one end of the optical fiber cable FC to be inspected, is connected to the connector-shaped connection portion 7. By the switching control of the optical switch 50, the first fixed length optical fiber 51 is selected as the optical path of the reference laser beam L2. By selecting the first fixed-length optical fiber 51, the optical path length of the reference laser light L2 becomes substantially equal to the optical path length to the connection portion 7 of the measurement laser light L1.

  Subsequently, in step S102, the measurement laser light L is emitted from the laser light source 2, and is split by the beam splitter 3 into the measurement laser light L1 to the measured connector C1 and the reference laser light L2 to the reference mirror 4 side. .

  In step S103, the reference optical path length by the reference laser beam L2 is moved within the variable range of the reference mirror 4 along the optical axis. The adjustment range of the optical path length is an extent corresponding to the optical distance from the connection portion 7 to the connector to be measured C1. Due to the movement of the reference mirror 4 of the reference optical system, the measurement optical path length to the defective part D1 in the connector C1 to be measured by the measurement laser light L1 matches the reference optical path length to the reference mirror 4 by the reference laser light L2. Sometimes, as shown in FIG. 3, a peak beat signal e is obtained by the interference light received by the optical measuring device 6.

In step S104, it is determined whether or not the optical beat measuring device 6 has received the peak beat signal e as described above. If the defective portion D1 does not exist in the connector C1 to be measured, the measurement laser light L1 is not reflected and returned to the optical measuring device 6, but is transmitted through the optical fiber cable FC. If the peak beat signal e is not detected, it is determined that the measured connector C1 is normal, the process proceeds to step S105, and the movement of the reference mirror 4 is stopped.
In step S106, the optical path selected by the optical switch 50 is switched from the first fixed length optical fiber 51 to the second fixed length optical fiber 52. By selecting the second fixed-length optical fiber 52, the optical path length of the reference laser light L2 becomes substantially equal to the optical path length of the measurement laser light L1 to the connector C2 to be measured. In step S107, the reference optical path length by the reference laser beam L2 is finely adjusted again by moving the reference mirror 4 along the optical axis. The adjustment range of the optical path length is an extent corresponding to the optical path length of the connector C2 to be measured. By the movement of the position of the reference mirror 4 of the reference optical system, the measurement optical path length to the defective portion D2 in the connector C2 to be measured by the measurement laser light L1 and the reference optical path length to the reference mirror 4 by the reference laser light L2 are obtained. When they coincide with each other, a peak beat signal e by interference light received by the optical measuring device 6 is obtained.
In step S108, it is determined whether or not the optical beat measuring device 6 has received the peak beat signal e as described above. If the defective portion D2 does not exist in the connector C2 to be measured, the measurement laser light L1 is not reflected and returned to the optical measuring device 6, but goes out from the connector C2 to be measured. If the peak beat signal e is not detected, it is determined that the connector to be measured C2 has no abnormality, the process proceeds to step S109, the movement of the reference mirror 4 is stopped, and the connector to be inspected attached to the optical fiber cable FC to be inspected. The measurement connector C1 and the connector to be measured C2 are both normal and are determined to be non-defective, and the inspection is terminated.
On the other hand, when the peak beat signal e is detected in step S104, it is determined that there is a disconnection failure due to the defective portion D1 in the connector C1 to be measured. FIG. 3 is a graph showing the distance of the defective portion D1 in the connector C1 to be measured, and the reflection level of interference light between the measurement laser light L1 ′ as the measurement optical system and the reference laser light L2 ′ as the reference optical system. FIG. For example, a state in which a defect such as disconnection occurs at a position of 10 mm in the connector to be measured C1 and the beat signal e described above appears in the corresponding optical path length of the reference optical system is shown.

  Since the magnitude of the peak beat signal e, that is, the reflection level is remarkably larger than the reflection level at a position where there is no defect, when the beat signal e is obtained, the peak beat signal e is present in the connector C1 to be measured. It is possible to easily determine that a defect such as a disconnection has occurred, and it is possible to specify a defective part as described above.

Since this measurement is based on a high-sensitivity interferometry, the reflection level of the beat signal e is remarkably increased even with a hidden disconnection in which only weak reflected light within the connector C1 is obtained. αdB can be obtained. The process proceeds to step S110, the movement of the reference mirror 4 is stopped, the measured connector C1 attached to the optical fiber cable FC to be inspected is determined to be defective, and the inspection ends.
If the peak beat signal e is detected in step S108, it is determined that there is a disconnection failure due to the defective portion D2 in the connector C2 to be measured. The detected peak beat signal e is the same as in the case of the defective portion D1 in the measured connector C1, and therefore the description thereof is omitted. The process proceeds to step S110, the movement of the reference mirror 4 is stopped, the measured connector C2 attached to the optical fiber cable FC to be inspected is determined to be defective, and the inspection is terminated.

  As described above, in the reflected light measurement device 1 of the first embodiment, once the optical fiber cable FC to be inspected is connected, it is attached to both ends of the optical fiber cable FC without changing the connection state. The measured connector C1 and the measured connector C2 can be inspected by a series of operations.

  Next, FIG. 4 shows the configuration of the reflected light measurement apparatus 1 of Example 2 when there are a plurality of optical fibers to be inspected. An optical path switching unit 8 is disposed between the beam splitter 3 and the connection unit 7 having a connector shape that can be connected to the measured connector C <b> 1 that is an MPO connector. The optical path switching unit 8 includes an optical switch, and the same number of optical path units as the number of fibers bundled in the MPO connector are disposed between the optical path switching unit 8 and the connection unit 7, and the optical switch of the optical path switching unit 8 is switched. These optical path portions can be switched by control.

  N optical fibers FM <b> 1 to FMn are bundled in the optical fiber cable FC to be inspected that is connected to the connection unit 7. For example, typically, 24 optical fibers are bundled.

  A measured connector C1, which is an MPO connector in which n optical fibers FM1 to FMn are bundled, is attached to one end of the optical fiber cable FC, and normal measured connectors C21 to C2n are attached to the other end.

  The optical path length of the first fixed-length optical fiber 51 is set to be substantially equal to the optical path length to the connection portion 7 of the measurement laser light L1. On the other hand, when the optical path length of the optical fibers FM1 to FMn is constant, the optical path length of the second fixed length optical fiber 52 is a value obtained by adding the optical path length of the first fixed length optical fiber 51 to the optical path length. It is set almost equal.

  When there are two or more optical path lengths of the optical fibers FM1 to FMn, two or more second fixed-length optical fibers 52 are prepared in advance so that the optical switch 50 can be selected. Keep connected. Or you may replace the 2nd fixed length optical fiber 52 during a measurement corresponding to the optical path length of optical fiber FM1-FMn. The other configuration of the reflected light measurement device 1 is the same as that of the first embodiment, and thus the description thereof is omitted.

  In the second embodiment configured as described above, the same procedure as the flowchart of FIG. 2 shown as the method for detecting the position of the defective optical connector according to the first embodiment can be adopted as the method for detecting the position of the defective position. .

  That is, by sequentially switching the optical fibers FM1 to FMn connected by the optical path switching unit 8, the same procedure as the flowchart shown in FIG. It is possible to detect defective portions D11 to D1n corresponding to FM1 to FMn and defective portions D21 to D2n corresponding to the connectors C21 to C2n to be measured by a series of operations.

  Accordingly, it is not necessary to individually attach the connectors to be measured C21 to C2n on the other end side branched into n pieces of the optical fibers FM1 to FMn, so that the inspection work is greatly reduced.

  In addition, although the reflected light measurement device 1 according to the second embodiment includes the optical path length switching unit 5 that switches the optical path length of the reference laser light L2 to a plurality of fixed lengths, the configuration may be omitted. In such a case, the object to be measured is only at one end side, and the defective portions D11 to D1n corresponding to the optical fibers FM1 to FMn in the connector to be measured C1 connected to the connection portion 7 can be diagnosed.

  In addition, the measurement target of the reflected light measurement device 1 of the second embodiment is described by exemplifying the optical fiber in the connector to be measured. However, in addition to the optical fiber in the connector to be measured, a glass plate, a contact lens, or the like It is also possible to diagnose a defective part of the material to be measured made of a translucent material. In such a case, a collimator is attached to the tips of the connectors to be measured C21 to C2n, and the reference laser light L2 ′ of each of the connectors to be measured C21 to C2n is referred to include the material to be measured arranged at the collimator tip. By adjusting the optical path length variable mechanism of the mirror 4, it is possible to diagnose a defective portion of the translucent material.

  As described in the first embodiment and the second embodiment, when a defective portion of the measured material made of a translucent material is not found by detecting the defect position by the interference method, there is a defect in the measured connector C. However, when a defective part is detected, it is necessary to further inspect the degree of the defect. In this case, by measuring the magnitude of the measurement laser beam L1 ′ that is the reflected light from the defective portion of the connector C to be measured obtained by the optical measuring device 6, that is, the reflection level αdB, A certain degree of failure such as disconnection can be estimated.

  However, the degree of failure such as disconnection of the connector C to be measured cannot be accurately quantified from the magnitude of the reflection level αdB. That is, even if the degree of failure is the same, the magnitude of the beat signal e obtained by the optical measuring instrument 6 is greatly influenced by individual characteristics such as the optical measuring instrument 6 and the amplifier circuit used, and the reflected light measurement is performed. This is because each device 1 is different.

  Therefore, in the reflected light measuring device 1, in order to universally quantify the reflectance for defects such as disconnection in the connector C to be measured, the light receiving characteristics of the light measuring device 6 of the reflected light measuring device 1 are used as a reference. Calibrate using an optical instrument or optical system. Then, the calibration line is held in the calculation control unit for each reflected light measuring device 1, and it is necessary to calibrate based on the output of the light measuring device 6 in the actual inspection by the reflected light measuring device 1.

  Although several methods can be considered for this calibration processing, the following explanation is one method. In the calibration process of the reflected light measurement device 1, first, a linear optical attenuator and a measured attenuation are evaluated using a separate optical attenuator as a reference.

  As shown in the block diagram of FIG. 5, this evaluation process is performed between a laser light source 2 equivalent to that used in the reflected light measuring device 1 and a reference light measuring device PD which is a commercially available power meter. The optical attenuator G is disposed. With respect to the reference light measuring device PD, a certain amount of light can be accurately measured due to its performance, but an extremely weak light amount of -50 dB or less cannot be measured.

  First, the attenuation factor of the optical attenuator G is set to 0 dB, the measurement laser light L1 is incident on the reference light measurement device PD, the light amount r0 is measured, the light amount r0 is set to 0 dB, and the zero reference point is set. Then, the light quantity r is measured while changing the set value of the optical attenuator G to change the attenuation rate.

  In this way, for the optical attenuator G to be the reference, the set value of the optical attenuator G is obtained using the reference light measuring device PD and the laser light source 2 equivalent to the reflected light measuring device 1. Obtain characteristic data of the relationship of attenuation.

  FIG. 6 is a graph showing the relationship between the set value of the X-axis optical attenuator G obtained as described above and the measured value of the Y-axis reference light measuring device PD, and has characteristic data having linearity. The following reference light amount reference setting process is performed using the optical attenuator G having

  As shown in FIG. 7, the optical attenuator G is arranged between the calibration reflection measuring device S and the calibration connector C ′ for performing the reference setting process of the reflected light amount. This calibration connector to be measured C 'has no defective portion, and a reflection mirror M that performs total reflection is disposed behind the calibration connector to be measured C'.

  The calibration reflection measuring device S includes a laser light source and a reference light measuring device (not shown), and a measurement value indicating a reflectance is obtained from the light amount of the measurement laser light L1 ′ received with respect to the light amount of the measurement laser light L1. It can be measured.

  The measurement laser light L1 passes through the optical attenuator G and the calibration target connector C ′, passes through the measurement laser light L1 ″ that totally reflects the reflection mirror M, and creates the measurement laser light L1 ′ as the reference reflected light.

  Note that the set value of the optical attenuator G is one direction in FIG. 5 and the reciprocating direction in FIG. 7, so that the attenuation rate is doubled in dB, but for ease of understanding. The attenuation factor is defined by the ratio of the first measurement laser beam L1 and the last measurement laser beam L1 ′ of the optical attenuator G and expressed as a set value.

  In the reference setting process of the reflected light amount, the optical attenuator is set so that the light amount received by the calibration reflection measuring device S is −14.7 dB, which is a reflectance between a cut surface of a typical optical fiber and air. Adjust the set value of G. Then, the set value of the optical attenuator G at this time is stored as the set value g from which the reference reflected light amount value −14.7 dB is obtained.

  That is, the set value g of the optical attenuator G is set to a value higher than −14.7 dB, for example, g = 1−13.7 dB due to the loss of the measurement optical system such as the calibration target connector C ′ and the reflection mirror M. At this time, the amount of reflected light received by the calibration reflection measuring device S is measured to be -14.7 dB, and the set value g of -13.7 dB is held. Note that the difference between the set value g of the optical attenuator G and the attenuation rate of the actual reflected light amount is caused by the loss of the measurement optical system, so that it always becomes a constant value even if the light amount of the measurement laser light L1 changes. I know.

  In this way, the optical attenuator G, the calibration-measured connector C ′, and the reflection mirror M in which the reference amount of the reflected light amount is set so that the measurement laser beam L1 ′ with respect to the measurement laser beam L1 becomes −14.7 dB are used. Thus, calibration of the light receiving characteristics of the light measuring device 6 of the reflected light measuring device 1 is performed.

  The optical attenuator G, the connector to be measured C ′ for calibration, and the reflection mirror M are connected to the reflected light measurement device 1 in which the optical path length switching unit 5 is the first fixed length optical fiber 51 as shown in FIG. Calibration data is obtained for each reflected light measuring device 1. When the calibration is performed, the measurement optical path length to the reflection mirror M by the measurement laser light L1 and the reference optical path length to the reference mirror 4 by the reference laser light L2 are set to coincide with each other.

  In this state, a virtual line that is a calibration line is obtained using a voltage value obtained when the optical measuring device 6 receives the interference light including the reflected light amount of the measurement laser beam L1 ′ of −14.7 dB set as a reference. Create P. In FIG. 9, the horizontal axis indicates the attenuation rate of the reflected light amount, and the vertical axis indicates the voltage v of the light amount received by the optical measuring device 6.

  In the configuration of FIG. 8, a reference voltage V1 obtained when the interference measuring light including the reflected light amount of −14.7 dB received by the optical measuring device 6 is set as a voltage V1, and this voltage V1 is set as a reference point β1 in FIG. Plot on the graph shown. In the figure, the bracket of -14.7 dB on the horizontal axis of the reference point β1 represents the set value of the optical attenuator G corresponding to the attenuation factor.

  Then, the voltage V0 of the optical measuring device 6 corresponding to the attenuation rate of the reflected light amount of −10 dB is calculated from the voltage V1, and this voltage V0 is set to −10 dB on the vertical axis. An intersection point of the attenuation rate −10 dB and the voltage V0 is set as a starting point β0, and an imaginary line P is drawn so as to pass through the starting point β0 and the reference point β1.

  If the virtual line P obtained in this way is stored in the arithmetic control unit, the amount of reflected light on the virtual line P is attenuated with respect to the output voltage obtained by the optical measuring device 6 of the reflected light measuring device 1. It is possible to output the rate, that is, the reflection level.

  In addition, the virtual line P is linearized by calculating the starting point β0 from only one reference point β1 as described above, but the set value of the optical attenuator G shown in FIG. The rate is adjusted to −10 dB, the voltage V2 at that time is measured, and the intersection of the attenuation rate −10 dB and the voltage V2 is defined as a measurement starting point β2. Thus, two or more measurement points may be obtained, and the virtual line P ′ may be drawn so as to pass through the measurement starting point β2 and the reference point β1. Since the virtual line P ′ uses the measurement value also at the measurement starting point β2, it is possible to increase the accuracy compared to the virtual line P.

  Thus, if the obtained virtual line P ′ is stored in the arithmetic and control unit, the output voltage corresponding to the interference light obtained by the light measuring device 6 of the reflected light measuring device 1 is more accurate. It is possible to output the reflectivity of a high reflected light amount, that is, the reflection level.

  Furthermore, since there is a possibility that a deviation occurs between the inclination a of the virtual line P ′ and the inclination of the virtual line P, the virtual line P ′ is calibrated by multiplying the virtual line P ′ by the reciprocal 1 / a of the inclination a. You may do it.

  In the above description, the reflected light measuring device 1 is described as being provided with, for example, one amplifier circuit. However, when the reflectance is actually small, the reflected light measuring device 1 has a larger number of, for example, 4 Two amplifier circuits are connected in series, and these are used while switching.

  For example, only one amplifier circuit is -10 to -40 dB, two connected amplifier circuits are -30 to -60 dB, three connected amplifier circuits are -50 to -80 dB, and four connected amplifier circuits. Then, it is measured while automatically switching the gain range such as −70 to −100 dB. As described above, when a plurality of amplifier circuits are used, it is necessary to obtain a calibration line based on individual electrical characteristics for each of the plurality of amplifier circuits with respect to the virtual line P set by only one amplifier circuit. is there.

  In the calibration method, first, when switching to the connection of two amplifier circuits, the set value g of the optical attenuator G is set so that the attenuation rate is -30 dB, and the optical measurement device is changed while appropriately changing the attenuation rate to -60 dB. Record the voltage v of 6. In this way, a plurality of recording points can be represented in the graph.

  Then, each recording point is recorded as γ1 dB, γ2 dB,... Which is a difference from the virtual line P, and an average difference value γdB is calculated. For example, when the average difference value γdB becomes +1 dB, a calibration line Q that is shifted by 1 dB from the virtual line P can be obtained as correction data.

  That is, in the measurement state shown in FIG. 1, when there are two amplifier circuits, an output along the calibration line Q shown in FIG. 9 is obtained, and when the three amplifier circuits are connected, four additional circuits are connected. Repeating the connection, the average difference value γdB is calculated and each calibration line Q is obtained. The arithmetic control unit stores the virtual line P and one or more calibration lines Q. Instead of the calibration line Q, an average difference value γdB with respect to the virtual line P may be stored.

  In this way, the arithmetic control unit can output the reflectance of the reflected light amount, that is, the reflection level, from the virtual line P or the calibration line Q corresponding to the measured voltage v.

  As described above, in the present embodiment, the virtual line P and the calibration line Q are stored in advance in the calculation control unit of the reflected light measurement apparatus 1, and the measured connector C1 and the measured connector C2 are connected as shown in FIG. Then, as described above, while changing the reference optical path length of the reference optical system, a defective part such as a disconnection in the measured connector C1 and the measured connector C2 is searched.

  If a defective part such as disconnection is not found, it is regarded as a non-defective product. If a defective part is detected, the virtual line P or the calibration line Q is applied to the output voltage of the interference light measured by the optical measuring device 6. By reading the reflectance of the amount of reflected light based on this, the reflectance with respect to the measurement laser light L1 at the defective portion can be converted into a numerical value and output.

  Furthermore, it is possible to guarantee to the user how much the reflectance of the defective state has been inspected. For example, a disconnection of up to −80 dB, which is a limit measurement value of the reflected light measuring device 1 for a connector to be sold, etc. As for the defective state, it can be guaranteed as a manufacturer that it was not found.

DESCRIPTION OF SYMBOLS 1 Reflected light measuring device 2 Laser light source 3 Beam splitter 4 Reference mirror 5 Optical path length switching part 50 Optical switch 51 1st fixed length optical fiber 52 2nd fixed length optical fiber 6 Optical measuring device 7 Connection part 8 Optical path switching part C1 , C2, C11, C21, C1n, C2n Connector to be measured FC Optical fiber cable FM Optical fiber PD Reference light measuring device G Optical attenuator S Calibration reflection measuring device M Reflecting mirror

Claims (7)

A laser light source that emits laser light; a measurement laser light that transmits the laser light; a beam splitter that branches into a reference laser light that reflects; a connection portion that is disposed on an optical path of the measurement laser light that has passed through the beam splitter; A reference mirror having an optical path length variable mechanism capable of adjusting an optical path length of the reference laser light, the measurement laser light reflected at a defective portion of the material to be measured made of a translucent material, and the reference reflected by the reference mirror A light measuring device for receiving laser light through the beam splitter,
In the reflected light measuring device for detecting the defective portion based on the reference laser light received by the light measuring device and the interference light by the measuring laser light,
A reflected light measuring apparatus, wherein a switching unit that switches an optical path of the reference laser light is disposed between the beam splitter and the reference mirror. The switching unit includes a first fixed-length optical fiber having an optical path length for a connector to be measured at one end of the optical fiber, and a second fixed-length light having an optical path length for the connector to be measured at the other end of the optical fiber. The reflected light measuring device according to claim 1, wherein the reflected light measuring device is an optical path length switching unit for switching between fibers.   The reflected light measurement according to claim 2, wherein the optical path length switching unit includes an optical switch, and switches the first fixed-length optical fiber or the second fixed-length optical fiber by switching control of the optical switch. apparatus. The measured material is an optical fiber in the connector under measurement, reflected light measurement device according to any one of claim 1 to 3, characterized in that connecting the measured connector to the connection portion. Stores the measurement value of the interference laser beam by the measurement laser beam obtained by attenuating incident light with a predetermined attenuation rate and the reference laser beam , and a virtual line with the predetermined attenuation rate as a reference point When the defective portion in the measured connector is detected based on the interference light generated by the measurement laser light and the reference laser light reflected at the defective portion, the interference light is supported based on the virtual line. the reflectance corresponding to the attenuation factor to the calculated reflected light measuring apparatus according to any one of claims 1 to 4, characterized in that connecting the arithmetic control unit which digitizes. The measurement value of interference light by the measurement laser beam attenuated by varying the attenuation factor and the reference laser beam, and the attenuation factor are measurement points, and the virtual line is the reference point The reflected light measuring apparatus according to claim 5 , wherein the line passes through two or more measurement points including
Light measuring device. The arithmetic control unit, when using a plurality of amplifier circuits connected in series, according to the number of a plurality of amplifier circuits of the optical measuring device obtained while varying the attenuation factor of the optical attenuator A calibration line based on an average difference value from the virtual line is stored for the measurement value, and the virtual line or the calibration according to the number of the amplification circuits with respect to the magnitude of the measurement value of the optical measuring device The reflected light measurement apparatus according to claim 5 or 6 , wherein the reflectance obtained from a line is calculated and digitized.

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