JP4250070B2 - Optical sensor - Google Patents

Description

  The present invention relates to an optical sensor in which a physical quantity detection medium is combined with a Michelson interferometer or a Mach-Zehnder interferometer, and more particularly to an optical sensor that can simplify a control signal line of a modulator.

An optical sensor in which a physical quantity detection medium is combined with a Mach-Zehnder interferometer is known. The optical sensor shown in FIG. 16 includes a light source 161 and a Mach-Zehnder that splits the light from the light source 161 into two optical paths (referred to as an optical path S) 162 and an optical path (referred to as an optical path L) 163 and combines them again. An interferometer 164, a physical quantity detection medium 165 attached to one of the optical paths S162 (or optical path L163) in the Mach-Zehnder interferometer 164 to give a phase change corresponding to the physical quantity to be detected to the light, and the Mach-Zehnder The interferometer 164 includes a modulator 166 that is inserted into at least one of the modulation optical paths and modulates light based on an electrical signal, and a light receiver 167 that receives light from the Mach-Zehnder interferometer 164. The optical demultiplexer 169 of the Mach-Zehnder interferometer 164 is connected to the optical transmission path 168 that guides the light from the light source 161, and the optical transmission path that guides the light to the light receiver 167 in the optical multiplexer 170 of the Mach-Zehnder interferometer 164. 171 is connected. The optical path length of the optical path S162 is L _S , and the optical path length of the optical path L163 is L _L.

The light having the coherent length L _C emitted from the light source 161 passes through the optical transmission path 168, and then is branched into the optical path S162 and the optical path L163 by the optical demultiplexer 169. Since the physical quantity detection medium 165 is disposed in the optical path S162, the optical path S162 changes in optical path length or refractive index in accordance with the physical quantity. On the other hand, since the modulator 166 is disposed in the optical path S162, the light passing therethrough is subjected to optical modulation corresponding to a change in optical path length or a change in refractive index based on an electrical signal. Light passing through both optical paths 162 and 163 is mixed by the optical multiplexer 170. When the optical path length L _S , the optical path length L _L, and other common optical path lengths satisfy Expression (1) and the polarization directions of both the optical paths 162 and 163 coincide, optical interference occurs.

| L _S −L _L | ≦ L _C (1)

  By controlling the modulator 166, only the optical interference intensity can be separated. From this optical interference intensity, the optical path length change or refractive index change by the physical quantity detection medium 165 can be accurately measured.

Japanese Examined Patent Publication No. 7-81888 Japanese Patent No. 2578601

  A measurement system using the optical sensor of FIG. 16 is shown in FIG. This measurement system includes a detection unit 173 including the Mach-Zehnder interferometer 164 portion of the optical sensor described in FIG. 16, and a control unit 174 including a light source 161 and a light receiver 167. The detection unit 173 and the control unit 174, an optical transmission path 168 connecting the light source 161 and the optical demultiplexer 169, an optical transmission path 171 connecting the optical multiplexer 170 and the optical receiver 167, and a signal line for transmitting a control signal to the modulator 166. 175 is provided.

  When the distance between the control unit 174 and the detection unit 173 is increased, there is a problem in that the measurement accuracy is deteriorated because the control signal transmitted through the signal line 175 is delayed.

  FIG. 18 shows a multipoint measurement system using a plurality of optical sensors of FIG. In this measurement system, a plurality of detection units 173a and 173b are provided for one control unit 174 described in FIG. The plurality of detectors 173a and 173b can be connected in parallel to the optical transmission lines 168 and 171 or in series. That is, it is only necessary to have two optical transmission paths 168 and 171 for multipoint measurement.

  However, two signal lines 175a and 175b are required to transmit control signals to the modulators 166a and 166b of the detection units 173a and 173b. The number of modulators 166a and 166b is also required as many as the number of detectors 173. Due to these necessary members, there is a problem that the cost becomes high.

  When a Michelson interferometer is used instead of the Mach-Zehnder interferometer 164 for the detection unit 173, one branched optical path S162 (or optical path L163) is used as the optical transmission path 168 (or optical transmission path 171). The modulator 166 can be disposed in the control unit 174, and the signal line for transmitting the control signal can be shortened. However, in this configuration, since one optical path inside the Michelson interferometer is used as an optical transmission path to the control unit 174, if the length of the optical transmission path is changed due to the installation of the detection unit 173, The length of the other optical path inside the Michelson interferometer also needs to be changed. That is, the control unit and the detection unit are not completely separated from each other.

  Accordingly, an object of the present invention is to provide an optical sensor that can solve the above-described problems and can simplify a control signal line of a modulator.

In order to achieve the above object, the present invention provides a light source, a plurality of detection optical interferometers for branching the light from the light source into two detection optical paths and recombining them, and each of the detection optical interferometers. A physical quantity detection medium that is attached to one of the detection optical paths and gives the light a phase change corresponding to the physical quantity of the detection target, and a plurality of optical multiplexers that combine the light from each of the detection optical interferometers, An optical transmission path for transmitting the light combined by the plurality of optical multiplexers, and one modulation optical interferometer for branching the light from the optical transmission path into two modulation optical paths and recombining them A modulator that is inserted into a modulation optical path in the modulation optical interferometer and modulates light, and a light receiver that receives light from the modulation optical interferometer, the light source and the light receiver And a modulation optical interferometer are arranged in close proximity to each other, and the detection unit is remote from the control unit. An optical interferometer is disposed, and one optical transmission path for reciprocating light from the control unit to the detection optical interferometer is laid, and the light from the light source is transmitted to the control unit side of the optical transmission path. And a control unit optical multiplexer / demultiplexer that guides the light from the optical transmission path to the modulation optical interferometer .

  The detection optical interferometer includes a detection optical multiplexer / demultiplexer for branching light from a light source into two detection optical paths and combining and extracting reflected return light from these detection optical paths, and the two paths And two reflectors for reflecting light from the respective ends of the detection optical path.

  The modulation optical interferometer includes: an optical multiplexer / demultiplexer that branches the light from the detection optical interferometer into two modulation optical paths and combines and extracts the reflected return light from the modulation optical paths; Two reflectors that reflect light from the respective ends of the two modulation light paths may be provided.

  The present invention exhibits the following excellent effects.

  (1) The control signal line of the modulator can be simplified.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the optical sensor according to the present invention is a light source 1 and a detection optical interferometer that splits light from the light source 1 into two detection optical paths 2 and 3 and combines them again. A detection Mach-Zehnder interferometer 4, a physical quantity detection medium 5 attached to one of the detection optical paths 2 in the detection Mach-Zehnder interferometer 4 to give light a phase change corresponding to a physical quantity to be detected, and a detection The modulation Michelson interferometer 8 that splits the light from the Mach-Zehnder interferometer 4 into the two modulation optical paths 6 and 7 and combines them again, and at least one of the modulation Michelson interferometers 8 A modulator 9 inserted in the optical path 6 for modulating light and a light receiver 10 for receiving light from the modulating Michelson interferometer 8 are provided.

  The detection Mach-Zehnder interferometer 4 splits the light from the light source 1 into two detection optical paths 2 and 3 and the light from these two detection optical paths 2 and 3. And an optical multiplexer 12 for multiplexing.

  The modulation Michelson interferometer 8 branches the light from the detection Mach-Zehnder interferometer 4 into two modulation optical paths 6 and 7 and combines the reflected return lights from the modulation optical paths 6 and 7. And an optical multiplexer / demultiplexer 13 to be extracted, and two reflectors 14 and 15 for reflecting light from the respective ends of the two modulation optical paths 6 and 7.

  An optical demultiplexer 11 of the Mach-Zehnder interferometer 4 is connected to the optical transmission path 16 that guides light from the light source 1, and an optical multiplexer / demultiplexer of the Michelson interferometer 8 for modulation is connected to the optical multiplexer 12 of the Mach-Zehnder interferometer 4. An optical transmission path 17 that guides light to the optical receiver 13 is connected, and an optical transmission path 18 that guides light to the optical receiver 10 is connected to the optical multiplexer / demultiplexer 13.

The detection optical path 2 provided with the physical quantity detection medium 5 is called an optical path S2, and the detection optical path 3 is called an optical path L. The optical path length of the optical path S2 is L _S , and the optical path length of the optical path L163 is L _L. The modulation optical path 6 provided with the modulator 9 is called an optical path Mod6, and the modulation optical path 7 is called an optical path M7. The optical path length of the light path MOD6 L _Mod, the optical path length of the light path M7 and L _M.

The light of the coherent length L _C emitted from the light source 1 passes through the optical transmission path 16 and then is branched into the optical path S2 and the optical path L3 by the optical demultiplexer 11. Since the physical quantity detection medium 5 is disposed in the optical path S2, the optical path S2 changes in optical path length or refractive index in accordance with the physical quantity. The light that has passed through both optical paths 2 and 3 is multiplexed by the optical multiplexer 12. Even if the optical path length L _S and the optical path length L _L satisfy the expression (2) and the polarization directions of both the optical paths 2 and 3 coincide with each other, no optical interference occurs.

| L _S −L _L | >> L _C (2)

Thereafter, the light passes through the optical transmission path 17 and is branched into the optical path Mod6 and the optical path M7 by the optical multiplexer / demultiplexer 13. The branched lights are reflected by the reflectors 14 and 15 and returned to the optical multiplexer / demultiplexer 13 to be multiplexed. At this time, optical interference occurs only when the optical path length L _S , the optical path length L _L , the optical path length L _Mod, and the optical path length L _M satisfy Expression (3).

| L _S + 2 × L _Mod −L _L + 2 × L _M | ≦ L _C (3)

Since light passes through the optical path Mod6 and the optical path M7 twice by reflection at the reflectors 14 and 15, the optical path length L _Mod and the optical path length L _M are doubled. Since the optical path lengths in the optical transmission path 16 and the optical transmission path 17 are common regardless of the optical path in each optical interferometer, they are eliminated.

  By controlling the modulator 9, only the optical interference intensity can be separated. From this optical interference intensity, the optical path length change or refractive index change by the physical quantity detection medium 5 can be accurately measured.

  The present invention can be applied to a magneto-optical sensor using a Lorentz force with respect to an electric current. That is, the detection optical path 2 is constituted by an optical fiber, and the optical fiber is coated with a conductive substance such as a metal such as gold or nickel or a conductive plastic as the physical quantity detection medium 5. An optical fiber is wound in a coil shape together with the physical quantity detection medium 5. When a time-varying current is passed through the physical quantity detection medium 5 wound in a coil shape, a Lorentz force corresponding to a magnetic field that is a physical quantity to be detected is generated in the coil, that is, the optical fiber. Due to the distortion, the optical path length of the detection optical path 2 changes. Therefore, the optical interference in the detection optical interferometer (the detection Mach-Zehnder interferometer 4 or the detection Michelson interferometer 61 described later) changes due to the change in the optical path length. The magnitude of the magnetic field can be detected from the change in the output of the light receiver 10 corresponding to the change in the optical interference.

  A measurement system using the optical sensor of the present invention shown in FIG. 1 is shown in FIG. The measurement system includes a detection Mach-Zehnder interferometer 4 and a control unit 19 including a light source 1, a light receiver 10, and a modulation Michelson interferometer 8. Between these, there are an optical transmission path that reciprocates between them, that is, an optical transmission path 20 that connects the light source 1 and the optical demultiplexer 11, and an optical transmission path 21 that connects the optical multiplexer 12 and the Michelson interferometer 8 for modulation. It is laid. The control unit 19 is provided with a modulator control device 22 that controls the modulator 9. The members constituting the modulation Michelson interferometer 8 are the same as those in FIG.

  In the optical sensor of the present invention, the detection Mach-Zehnder interferometer 4 provided with the physical quantity detection medium 5 and the modulation Michelson interferometer 8 provided with the modulator 9 are separately configured. The modulator 9 can be placed together with the light source 1 and the light receiver 10 as in the system, and the optical transmission path 20, the remote detection Mach-Zehnder interferometer 4 in which the physical quantity detection target exists. Only the control signal line 21 for the modulator 9 need not be installed. For this reason, even if the distance between the detection Mach-Zehnder interferometer 4 and the control unit 19 is increased, the control signal of the modulator 9 is not deteriorated, and the measurement accuracy can be maintained high.

  In the measurement system of FIG. 2, the optical path lengths in the round trip optical transmission paths 20 and 21 are the same regardless of the optical path in each optical interferometer, and therefore do not affect the equation (3). Therefore, even if the lengths of the optical transmission lines 20 and 21 are changed, it is not necessary to change the lengths of the optical paths in the optical interferometers 4 and 8. If the optical path length difference is maintained even if the optical path length in the modulation Michelson interferometer 8 in the control unit 19 changes, the length of each optical path of the detection Mach-Zehnder interferometer 4 needs to be changed. There is no. That is, the detection Mach-Zehnder interferometer 4, the control unit 19, and the optical transmission lines 20 and 21 are completely independent, and can be individually replaced without affecting each other.

  Further, the present invention has an advantage in multipointing. That is, a plurality of detection Mach-Zehnder interferometers 4 can be connected to the reciprocating optical transmission lines 20 and 21 in parallel or in series. Even if the number of points is increased, only one modulator 9 is required, and a control signal line for the modulator 9 does not need to be provided, so that the cost does not increase.

  A multipoint measurement system using a plurality of the optical sensors of FIG. 1 is shown in FIGS.

  In the multipoint measurement system of FIG. 3, a plurality of detection Mach-Zehnder interferometers 4 are connected in parallel at intervals to the reciprocating optical transmission lines 20 and 21 from the same control unit 19 as in FIG. More specifically, the incident side of the first detection Mach-Zehnder interferometer 4a is connected to the optical demultiplexer 31a provided in the middle of the optical transmission path 20, and the optical multiplexer 32a provided in the middle of the optical transmission path 21. Are connected to the emission side of the first detection Mach-Zehnder interferometer 4a, and the second and third detection Mach-Zehnder interferometers 4b and 4c are incident on the optical demultiplexer 31b provided at the end of the optical transmission line 20. The output sides of the second and third detection Mach-Zehnder interferometers 4b and 4c are connected to an optical multiplexer 32b provided at the end of the optical transmission line 21. Of course, there is no limit to the number of detection Mach-Zehnder interferometers 4 to be connected.

  In the multipoint measurement system of FIG. 4, a plurality of detection Mach-Zehnder interferometers 4 are connected in series to the reciprocating optical transmission lines 20 and 21 from the same control unit 19 as in FIG. More specifically, the incident side of the first Mach-Zehnder interferometer 4a for detection is connected to the optical transmission line 20, and the incident side of the second Mach-Zehnder interferometer 4b for detection is connected to the emission side of the Mach-Zehnder interferometer 4a for detection. As described above, the incident side and the emission side of the detection Mach-Zehnder interferometer 4 are sequentially connected, and the optical transmission path 21 is connected to the emission side of the third detection Mach-Zehnder interferometer 4c. Of course, there is no limit to the number of detection Mach-Zehnder interferometers 4 to be connected.

  In the multipoint measurement system as shown in FIGS. 3 and 4, the configuration shown in FIG. 5 may be used to separate the light returned from the optical transmission path 21. That is, the difference between the optical path lengths of the two detection optical paths 2 and 3 in the first, second, and third detection Mach-Zehnder interferometers 4a, 4b, and 4c (see FIGS. 3 and 4) is the detection Mach-Zehnder. On the other hand, in the control unit 19, as shown in FIG. 5, the optical path length difference between the two modulation optical paths 6 and 7 is determined by each control Mach-Zehnder interferometer 4a, A plurality of extra-length optical paths 51a, 51b, 51c for equalizing the optical path length difference between the two detection optical paths 2 and 3 in 4b, 4c, and an optical switch 52 for switching the extra-length optical paths 51a, 51b, 51c. The optical switch 52 is provided at the end of the modulation optical path 7 without the modulator, and the reflectors 15a, 15b, and 15c are provided at the ends of the extra length optical paths 51a, 51b, and 51c, respectively.

Here, the optical path length differences between the two detection optical paths 2 and 3 in each of the detection Mach-Zehnder interferometers 4a, 4b, and 4c are Δa, Δb, and Δc. Further, the optical path length of the modulation optical path 6 is L _Mod , the optical path length obtained by adding the surplus optical path 51a and the modulation optical path 7 which are optical paths by switching the optical switch 52 is L _Ma , and the surplus optical path 51b and the modulation optical path 51b are used for modulation. The optical path length obtained by adding the optical path 7 is L _Mb , and the optical path length obtained by adding the extra length optical path 51 c and the modulation optical path 7 is L _Mc .

  At this time, optical interference can occur in the specific detection Mach-Zehnder interferometer 4 according to the equations (4) to (9).

| Δa ± 2 × (L _Mod −L _Ma ) | ≦ L _C ; satisfying any of ± (4)
| Δb ± 2 × (L _Mod −L _Mb ) | ≦ L _C ; satisfy any of ± (5)
| Δc ± 2 × (L _Mod −L _Mc ) | ≦ L _C ; satisfying any of ± (6)
| Δa ± 2 × (L _Mod −L _Mb ) | >> L _C ; both of ± are established (7)
| Δa ± 2 × (L _Mod −L _Mc ) | >> L _C ; both of ± are established (8)
| Δb ± 2 × (L _Mod −L _Mc ) | >> L _C ; both of ± are established (9)

  When there is an arbitrary natural number N of detection Mach-Zehnder interferometers 4, equations (4) to (9) are expressed by equation (10).

| Δj ± 2 × (L _Mod −L _Mk ) | ≦ L _C : j = k
| Δj ± 2 × (L _Mod −L _Mk ) | >> L _C : j ≠ k
0 <natural number j, k ≦ N (10)

  That is, if the optical path length difference between the two detection optical paths 2 and 3 in each detection Mach-Zehnder interferometer 4 and the optical path length of each extra-length optical path 51 in the modulation Michelson interferometer 8 are determined according to the above equation, By switching the optical switch 52, the light receiver 10 can measure the interference of the light that has passed through the arbitrary detection Mach-Zehnder interferometer 4.

When an SLD (super luminescent diode) is used as the light source 1, the coherent length L _{C of the} light source light is about 10 μm. On the basis of 10 times or more of the coherent length, if the optical path length difference between the detection Mach-Zehnder interferometers 4 is 0.1 mm or more away, optical interference does not occur. Therefore, even if the number of detection Mach-Zehnder interferometers 4 is 10, there are many combinations of extra-length optical paths that satisfy Expression (10).

  In the embodiments described so far, a Mach-Zehnder interferometer is used as the detection optical interferometer. In the next embodiment, a Michelson interferometer is used as the detection optical interferometer.

  As shown in FIG. 6, a light source 1 and a detection Michelson interferometer 61 as a detection optical interferometer that splits the light from the light source 1 into two detection optical paths 2 and 3 and combines them again. The physical quantity detection medium 5 that is attached to one of the detection optical paths 2 in the detection Michelson interferometer 61 and applies a phase change corresponding to the physical quantity to be detected to the light, and the light from the detection Michelson interferometer 61 Is modulated into at least one of the modulation optical paths 6 in the modulation Michelson interferometer 8. And a light receiver 10 that receives light from the modulation Michelson interferometer 8.

  A detection Michelson interferometer 61 which is a difference between FIG. 1 and FIG. 6 branches light from the light source 1 into two detection light paths 62 and 63 and reflects from the detection light paths 62 and 63. A detection optical multiplexer / demultiplexer 64 that multiplexes and extracts return light and two reflectors 65 and 66 that reflect light from the respective ends of the two detection optical paths 62 and 63 are provided. An optical transmission line 17 that guides light to the optical multiplexer / demultiplexer 13 of the modulation Michelson interferometer 8 is connected to the detection optical multiplexer / demultiplexer 64.

In this optical sensor, the light of the coherent length L _C emitted from the light source 1 passes through the optical transmission path 16 and then is branched into the detection optical paths 62 and 63 by the detection optical multiplexer / demultiplexer 64. Since the physical quantity detection medium 5 is disposed in the detection light path 62, the detection light path 62 changes in optical path length or refractive index in accordance with the physical quantity. The light incident on the detection optical paths 62 and 63 is reflected by the reflectors 65 and 66, returned to the detection optical multiplexer / demultiplexer 64, multiplexed, and guided to the modulation Michelson interferometer 8.

  A measurement system using the optical sensor of the present invention shown in FIG. 6 is shown in FIG. This measurement system includes a detection Michelson interferometer 61 and a control unit 19 including a light source 1, a light receiver 10, and a modulation Michelson interferometer 8, and the detection Michelson interferometer 61, the control unit 19, and the like. The optical transmission path that reciprocates between them, that is, the optical transmission path 20 that connects the light source 1 and the detection optical multiplexer / demultiplexer 64, and the detection optical multiplexer / demultiplexer 64 and the modulation Michelson interferometer 8 are connected. An optical transmission line 21 is laid.

  In this optical sensor or measurement system, light passes through the physical quantity detection medium 5 twice, so that the detection sensitivity is doubled compared to that in FIG.

  In the next embodiment, a single optical transmission line connecting the detection Michelson interferometer 61 and the control unit 19 is used. The optical sensor shown in FIG. 8 uses one optical transmission path 81 to unify the optical transmission paths 16 and 17 in FIG. 6, and guides the light from the light source 1 to the optical transmission path 81 and from the optical transmission path 81. Is provided with a control unit optical multiplexer / demultiplexer 82 that guides the light to the modulation Michelson interferometer 8. Unlike the detection optical multiplexer / demultiplexer 64 shown in FIG. 6, the detection optical multiplexer / demultiplexer 83 of the detection Michelson interferometer 61 transmits light from the optical transmission path 81 to the two detection optical paths 62 and 63. In addition to branching, the reflected return light from these detection light paths 62 and 63 is multiplexed and returned to the optical transmission path 81.

  As shown in FIG. 9, the measurement system using this optical sensor is provided with a single optical transmission path 91 for reciprocating light from the detection Michelson interferometer 61 to the control unit 19, and the light from the light source 1 is transmitted. A control unit optical multiplexer / demultiplexer 92 that guides the light from the optical transmission path 91 to the modulation Michelson interferometer 8 is provided in the control unit 19. Further, the detection optical multiplexer / demultiplexer 92 of the detection Michelson interferometer 61 is configured to return the light incident from the optical transmission path 91 and reflected and returned to the optical transmission path 91.

  In this optical sensor or measurement system, since the optical transmission path 91 connecting the detection Michelson interferometer 61 and the control unit 19 is one path, the optical transmission path 91 can be easily laid and a member as compared with the case of two paths. Can be saved.

  In the embodiments described so far, a Michelson interferometer is used as the modulation optical interferometer. In the following embodiment, a Mach-Zehnder interferometer is used as the modulation optical interferometer.

As shown in FIG. 10, an optical sensor according to the present invention is a light source 1 and a detection optical interferometer that splits light from the light source 1 into two detection optical paths 2 and 3 and combines them again. A detection Mach-Zehnder interferometer 4, a physical quantity detection medium 5 attached to one of the detection optical paths 2 in the detection Mach-Zehnder interferometer 4 to give light a phase change corresponding to a physical quantity to be detected, and a detection A modulation Mach-Zehnder interferometer 101 that splits light from the Mach-Zehnder interferometer 4 into two modulation optical paths 6 and 7 and combines them again, and at least one of the modulation Mach-Zehnder interferometers 101 A modulator 9 that is inserted into the optical path for modulating light and a light receiver 10 that receives light from the modulation Mach-Zehnder interferometer 101.

  The modulation Mach-Zehnder interferometer 101 combines the light from the optical transmission path 17 into the two optical paths 6 and 7 for modulation and the light from these optical paths 6 and 7 for modulation. And an optical multiplexer 103 for wave generation.

  As shown in FIG. 11, the measurement system using the optical sensor of FIG. 10 includes a detection Mach-Zehnder interferometer 4, a light source 1, a light receiver 10, and a control unit 111 including a modulation Mach-Zehnder interferometer 101. Consists of. The only difference from FIG. 2 is that the modulation Michelson interferometer 8 is replaced with the modulation Mach-Zehnder interferometer 101.

In this measurement system, optical interference occurs only when the optical path length L _S , the optical path length L _L , the optical path length L _Mod, and the optical path length L _M satisfy Expression (3 ′).

| L _S + L _Mod −L _L + L _M | ≦ L _C (3 ′)

Compared with equation (3), it can be seen that coefficient 2 is not included. Further, even when the number of points is increased, when a Mach-Zehnder interferometer is used as each detection optical interferometer, the equations (4 ′) to (9 ′) in which the coefficient 2 is not included in the equations (4) to (9),
| Δa ± (L _Mod −L _Ma ) | ≦ L _C ; satisfying any of ± (4 ′)
| Δb ± (L _Mod −L _Mb ) | ≦ L _C ; satisfying any of ± (5 ′)
| Δc ± (L _Mod −L _Mc ) | ≦ L _C ; satisfying any of ± (6 ′)
| Δa ± (L _Mod −L _Mb ) | >> L _C ; both of ± are established (7 ′)
| Δa ± (L _Mod −L _Mc ) | >> L _C ; both of ± are established (8 ′)
| Δb ± (L _Mod −L _Mc ) | >> L _C ; both of ± are established (9 ′)
Will be used.

  When there is an arbitrary natural number N of Mach-Zehnder interferometers 4 for detection, equation (10 ｀) is used instead of equation (10).

| Δj ± (L _Mod −L _Mk ) | ≦ L _C : j = k
| Δj ± (L _Mod −L _Mk ) | >> L _C : j ≠ k
0 <natural number j, k ≦ N (10 ｀)

  An optical sensor and a measurement system using a Michelson interferometer as a detection optical interferometer and a Mach-Zehnder interferometer as a modulation optical interferometer are shown in FIGS. In this embodiment, the detection Michelson interferometer 61 and the modulation Mach-Zehnder interferometer 101 described above are used, and the operation is obvious.

  Further, an optical sensor and a measurement system in which the optical transmission paths 16 and 17 (20, 21) in FIGS. 12 and 13 are one path are shown in FIGS. In this embodiment, optical transmission lines 81 and 91 similar to those shown in FIGS. 8 and 9 are used, and the operation is obvious.

  The present invention can also be applied to reflection tomographic image measurement using low coherence light used for fundus image measurement and the like. The present invention can also be applied to refractive index measurement using optical fiber gyroscope and optical heterodyne measurement.

  Furthermore, the present invention can be applied as a one-to-many communication device by using an optical phase modulator or the like as the physical quantity detection medium 5.

It is a block diagram of the optical sensor which shows one Embodiment of this invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is an internal block diagram of the control part of the measurement system of FIG. 3, FIG. It is a block diagram of the optical sensor which shows one Embodiment of this invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is a block diagram of the optical sensor which shows one Embodiment of this invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is a block diagram of the optical sensor which shows one Embodiment of this invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is a block diagram of the optical sensor which shows one Embodiment of this invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is a block diagram of the optical sensor which shows one Embodiment of this invention. It is a lineblock diagram of a measurement system showing one embodiment of the present invention. It is a block diagram of the optical sensor of background art. It is a block diagram of the measurement system of background art. It is a block diagram of the measurement system of background art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2,3 Optical path for detection 4 Optical interferometer for detection 5 Physical quantity detection medium 6,7 Optical path for modulation 8 Optical interferometer for modulation 9 Modulator 10 Light receiver

Claims (3)

A light source, a plurality of detection optical interferometers for splitting the light from the light source into two detection optical paths and recombining them, and one of the detection optical interferometers attached to one of the detection optical paths A physical quantity detection medium that gives the light a phase change corresponding to the physical quantity to be detected, a plurality of optical multiplexers that combine the light from each of the detection optical interferometers, and a plurality of optical multiplexers An optical transmission path for transmitting light, one modulation optical interferometer for splitting the light from the optical transmission path into two modulation optical paths and recombining, and the modulation optical interferometer A modulator that is inserted into the modulation optical path and modulates the light; and a light receiver that receives light from the modulation optical interferometer ,
A control unit is configured in which the light source, the light receiver, and the modulation optical interferometer are arranged close to each other, and the detection optical interferometer is arranged remotely from the control unit, and the detection from the control unit One optical transmission path for reciprocating light to the optical interferometer is laid, and the light from the light source is guided to the optical transmission path on the control unit side of the optical transmission path, and the light from the optical transmission path is modulated. An optical sensor characterized in that an optical multiplexer / demultiplexer for a control unit that leads to is provided .   The detection optical interferometer includes a detection optical multiplexer / demultiplexer for branching light from a light source into two detection optical paths and combining and extracting reflected return light from these detection optical paths, and the two paths The optical sensor according to claim 1, further comprising: two reflectors that reflect light from respective ends of the detection optical path.   The modulation optical interferometer includes: an optical multiplexer / demultiplexer that branches the light from the detection optical interferometer into two modulation optical paths and combines and extracts the reflected return light from the modulation optical paths; The optical sensor according to claim 1, further comprising two reflectors that reflect light from respective ends of the two paths of the modulation light paths.

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