JPH04305111A - Method for measuring elongation of light compound overhead earth wire - Google Patents

Abstract

PURPOSE:To enable an elongation at a specific section of a light compound overhead earth wire to be measured accurately without increasing measurement error even if a measurement section of an optical fiber within the light compound overhead earth wire is away from a measurement system. CONSTITUTION:A light measurement signal Oms propagates an optical fiber for measurement 12 of a light compound overhead earth wire 10 and converts a reference signal to a light reference signal Ors, this light reference signal Ors propagates a transmission path of an optical fiber for reference 14 corresponding to the same length as a portion other than a measurement section Dm out of light signal propagation path according to the optical fiber for measurement 12 and then converts these signals into electrical signal by light/electricity converters 20A and 20B and then feeds it to a phase difference meter 22, thus enabling an elongation of the optical fiber for measurement 12 to be measured by the phase method. A change in phase due to change in length of the optical fiber which is generated at a portion other than the measurement section Dm out of the optical signal propagation path according to the optical fiber for measurement 12 is canceled out by that in phase according to that in length of the optical fiber for reference signal 14.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for measuring the elongation of an optical composite overhead ground wire, and more specifically, an improvement in the method of measuring the elongation of an optical fiber in an optical composite overhead ground wire using the phase method. It is related to.

0002

[Prior art] The phase method for measuring the elongation of optical fibers is
An optical signal whose intensity is modulated into a sinusoidal wave at a certain frequency is propagated through an optical fiber, and when the length of the optical fiber changes, the time required for the optical signal to propagate through the optical fiber changes, and the optical signal is Since the phase of the optical signal changes, the amount of phase change of the optical signal on the receiving side is determined by comparing it with the phase of the reference signal, and the elongation of the optical fiber is calculated from the value of this amount of phase change.

[0003] When measuring the elongation of an optical fiber fixed type optical composite overhead ground wire, since the optical fiber is fixed in an aluminum pipe, the elongation of the optical composite overhead ground wire is approximately equal to the elongation of the optical fiber. it is conceivable that. Therefore, by measuring the elongation of the optical fiber using the above-mentioned phase method, the elongation of the optical composite overhead ground wire can be measured.

In an optical fiber elongation measuring system, an electrical signal from a signal generator is sent to two systems. 1
The two systems are electrical/
Other systems include optical converters and phase contrast meters that use electrical signals as reference signals. The optical signal propagates through the optical fiber of the optical composite overhead ground wire, is converted into an electrical signal by an optical/electrical converter, and is then compared in phase with a reference signal by a phase difference meter to determine the phase difference. When elongation occurs in the optical composite overhead ground wire and the optical fiber is stretched, the propagation time of the optical signal changes and the phase difference changes, and the elongation of the optical composite overhead ground wire is measured from the change in phase difference. be able to.

[0005]

[Problems to be Solved by the Invention] However, according to this prior art measurement method, the length of the optical fiber in the optical composite overhead ground wire through which the optical signal for measurement propagates is longer than the length of the optical fiber to be measured. If the optical composite overhead ground wire is physically separated from the measurement system, the optical fiber section connecting the measurement system and the optical composite overhead ground wire will become longer, and the length of the optical fiber between them will increase due to temperature changes, etc. The error in the elongation of the optical composite overhead ground wire increases. In addition, the conventional measurement method measures the elongation of the optical fiber between the electrical/optical converter and the optical/electrical converter, so it is not possible to measure the elongation of a specific section of the optical composite overhead ground wire. Ta.

An object of the present invention is to avoid the above-mentioned drawbacks, to enable measurement without increasing the measurement error even if the measurement section of the optical fiber and the measurement system are far apart, and to enable measurement to be performed without increasing the measurement error. An object of the present invention is to provide a method for measuring an optical composite overhead ground wire that can measure the elongation of a specific section of the wire.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the present invention propagates an optical signal whose intensity is modulated into a sine wave at a certain frequency in an optical fiber in an optical composite overhead ground wire, and In the method of measuring the elongation of an optical overhead ground wire by determining the elongation of the optical fiber from the change in the phase of the optical signal with respect to the phase, the optical reference signal obtained by converting the reference signal into an optical signal is used as the optical signal of the optical fiber for measurement. Optical fiber that propagates to the transmission path of the reference signal optical fiber corresponding to the same length as the part of the signal propagation path other than the measurement section, and that occurs in the part of the optical signal propagation path of the measurement optical fiber other than the measurement section. The optical composite overhead ground wire is characterized in that the elongation of the measurement section of the measurement optical fiber is measured by offsetting the phase change due to the length change of the reference signal optical fiber with the phase change due to the length change of the reference signal optical fiber. The object of the present invention is to provide a method for measuring elongation.

[0008]

[Operation] In this way, the reference signal is not sent directly to the phase difference meter, but instead is converted into an optical signal and the optical signal for measurement is propagated on a path other than the section where the elongation of the optical composite overhead ground wire is measured. If the signal is propagated along a path of the same length and then converted back into an electrical signal and sent to the phase difference meter, the elongation of the optical fiber that occurs in areas other than the measurement section where the elongation of the optical composite overhead ground wire is measured is canceled out. It is possible to measure only the elongation of the optical fiber that occurs in a specific section of the optical composite overhead ground wire.

[0009]

[Example] An embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 schematically shows an example of the elongation measuring method of an optical composite overhead ground wire according to the present invention. Line 10 is
A reference optical fiber 14 is included in addition to the measurement optical fiber 12. The elongation of the measurement section Dm of the measurement optical fiber 12 is measured using a phase method in which the phase of the optical measurement signal propagating through this measurement section Dm is compared with the phase of the reference signal and determined from the amount of phase change. In addition, in FIG. 1, the reference numeral 24 indicates a steel tower.

Electrical signal E transmitted from signal generator 16
s is converted by electric/optical converters 18A and 18B into two optical signals whose intensity is modulated into a sine wave of a certain frequency,
One optical signal is an optical reference signal Ors that propagates through the reference optical fiber 14, and the other optical signal is an optical measurement signal Oms that propagates through the measurement optical fiber 12.

The optical measurement signal Oms is transmitted to the optical composite overhead ground wire 10.
The optical reference signal O
rs is propagated to the reference optical fiber 14 of the optical composite overhead ground wire 10. The reference optical fiber 14 has a length corresponding to the section of the measurement optical fiber 12 excluding the measurement section Dm to be measured. Therefore, the reference optical fiber 14 has the same length as the optical signal propagation path of the measurement optical fiber 12 other than the measurement section Dm, and the reference optical fiber 14 propagates the optical reference signal Ors. Form a route.

The optical measurement signal Oms and the optical reference signal Ors propagated through the measurement optical fiber 12 and the reference optical fiber 14 are transmitted to optical/electrical converters 20A and 20B, respectively.
These electrical signals Ems and Ers are then sent to a phase difference meter 22, and this phase difference meter 22 calculates the elongation of the optical composite overhead ground wire 10 by the phase method. Measure.

As already mentioned, the transmission path by the reference optical fiber 14 through which the optical reference signal Ors propagates is the measurement section D of the optical signal propagation path by the measurement optical fiber 12.
Therefore, the phase change due to the change in the length of the optical fiber that occurs in the optical signal propagation path by the measurement optical fiber 14 other than the measurement section Dm is the same as the length of the reference signal. This is canceled out by a change in phase due to a change in the length of the optical fiber 14. Therefore, the phase difference meter 22 measures only the elongation of the measurement section Dm of the measurement optical fiber 12.

The measurement system shown in FIG. 2 includes a signal generator 16 of the measurement system.
and electric/optical converters 18A and 18B.
1 except that the optical/electrical converters 20A, 20B of the measurement system and the receiving section 26B including the phase difference meter 22 are arranged separately at both ends of the optical composite overhead ground wire 10. It is exactly the same as the example, and the same parts are designated by the same reference numerals. Furthermore, since the operation of this measurement system is exactly the same as that of the embodiment shown in FIG. 1, the explanation thereof will be omitted.

FIG. 3 shows another embodiment of the present invention in which the measuring optical fiber and the reference optical fiber are partially used. In this embodiment, the electrical signal Es transmitted from the signal generator 16 is
is converted into an intensity-modulated optical signal Os by one electrical/optical converter 18, and this optical signal Os is transmitted through a measurement/reference optical fiber 28 and then sent to a measurement optical fiber by an optical demultiplexer 30. 12A and a reference optical fiber 14A, and thereafter sent to a phase difference meter 22 via optical/electrical converters 20A and 20B similarly to the embodiment of FIG. The operation of the measurement system in this embodiment is also the same as that in the embodiment shown in FIG. 1, so its explanation will be omitted.

FIG. 4 shows yet another embodiment of the present invention in which the reference optical fiber is also used as the measurement optical fiber; in this embodiment, the electrical signal Es from the signal generator 16 is
are optical measurement signals O with different wavelengths that are intensity-modulated by the electrical/optical converters 18A and 18B with different wavelengths, respectively.
ms and an optical reference signal Ors, and these optical measurement signal Oms and optical reference signal Ors are combined by an optical multiplexer 32, propagated through a measurement/reference optical fiber 28A, and then passed through an optical demultiplexer. 34A, the optical measurement signal Oms and the optical reference signal Ors are separated again. The optical measurement signal Oms propagates through the measurement section Dm of the measurement optical fiber 12, and the optical reference signal Ors propagates through the extremely short connection optical fiber 36.
After being multiplexed by the optical multiplexer 38 with the optical measurement signal Oms that has propagated through the measurement section Dm through the optical multiplexer 38 and propagated through the measurement/reference optical fiber 28B, it is demultiplexed by the optical demultiplexer 40 and sent to the optical/electrical converter. The signal is sent to the phase difference meter 22 via 20A and 20B. The operation of the measurement system in this embodiment is also exactly the same as that in the embodiment shown in FIG. 1, so a description thereof will be omitted.

The embodiments shown in FIGS. 3 and 4 have a common feature in that part or all of the measurement optical fiber and the reference optical fiber are used in common, and an optical signal can be sent using a single fiber in the shared part. ing.

[0018]

According to the present invention, as described above, the reference signal is not sent directly to the phase difference meter, but is converted into an optical signal to measure the elongation of the optical composite overhead ground wire through a route other than the measurement section. The measurement optical signal is propagated along a path of the same length as the propagation path, and then converted back into an electrical signal and sent to a phase difference meter to be measured using the phase method. Phase changes caused by optical fiber elongation that occur in other parts are canceled out, so even if the distance between the measurement system and the measurement section is long, only the optical fiber elongation that occurs in a specific section of the optical composite overhead ground wire can be accurately measured. There are real benefits that can be well measured.

[Brief explanation of drawings]

FIG. 1 is a system diagram schematically showing an embodiment of a method for measuring the elongation of an optical composite overhead ground wire according to the present invention.

FIG. 2 is a system diagram schematically showing another embodiment of the method for measuring elongation of an optical composite overhead ground wire according to the present invention.

FIG. 3 is a system diagram schematically showing still another embodiment of the method for measuring elongation of an optical composite overhead ground wire according to the present invention.

FIG. 4 is a system diagram schematically showing still another embodiment of the method for measuring elongation of an optical composite overhead ground wire according to the present invention.

[Explanation of symbols]

10 Optical composite overhead ground wire 12 Optical fiber for measurement 14 Standard optical fiber 16 Signal generator 18 Electrical/optical converter 18A Electric/Optical Converter 18B Electricity/optical converter 20A optical/electrical converter 20B Optical/electrical converter 22 Phase difference meter 26A Transmitter 26B Receiving section 28 Optical fiber for measurement and reference 28A optical fiber for measurement and reference 28B Optical fiber for measurement and reference 30 Optical demultiplexer 32 Optical multiplexer 34 Optical demultiplexer 36 Optical fiber for connection 38 Optical multiplexer 40 Optical demultiplexer

Claims (1)

[Claims] 1. An optical signal whose intensity is sinusoidally modulated at a certain frequency is propagated through an optical fiber in an optical composite overhead ground wire, and the elongation of the optical fiber is determined from a change in the phase of the optical signal with respect to the phase of a reference signal. In the method for measuring the elongation of the optical composite overhead ground wire, the optical reference signal obtained by converting the reference signal into an optical signal is connected to a portion of the optical signal propagation path of the measurement optical fiber other than the measurement section. A change in phase due to a change in the length of the optical fiber that propagates in the transmission path of the reference signal optical fiber corresponding to the same length and occurs in a portion of the optical signal propagation path other than the measurement section by the measurement optical fiber. A method for measuring the elongation of an optical composite overhead ground wire, characterized in that the elongation of the measurement section of the measurement optical fiber is measured by offsetting a phase change due to a change in the length of the reference signal optical fiber.