Power coupling coefficient measuring method and power coupling coefficient measuring device
An object of the present disclosure is to provide a power coupling coefficient measurement method and a power coupling coefficient measurement device capable of inexpensively and easily measuring a power coupling coefficient. The power coupling coefficient measurement method according to the present disclosure is a power coupling coefficient measurement method for measuring a power coupling coefficient of a multi-core fiber in order to achieve the aforementioned object, and includes: inputting a test light pulse from one end of the multi-core fiber to any one of cores; receiving backscattered light of the core to which the test light pulse is input or any one of the other cores; measuring an intensity distribution of the backscattered light with respect to a distance from the one end of the multi-core fiber; and calculating the power coupling coefficient from the intensity distribution of the backscattered light.
1. A power coupling coefficient measurement method for measuring a power coupling coefficient of a multi-core fiber, comprising:
inputting a test light pulse from one end of the multi-core fiber to any one of cores;
receiving backscattered light of the core to which the test light pulse has been input or any one of the other cores;
measuring an intensity distribution of the backscattered light with respect to a distance from the one end of the multi-core fiber; and
calculating a power coupling coefficient from the intensity distribution of the backscattered light,
wherein the calculating of the power coupling coefficient further includes:
representing the intensity distribution in a logarithm;
calculating an approximate intensity distribution of a linear expression with respect to the distance on the basis of the intensity of the backscattered light in a region where the logarithm of the intensity distribution can be approximated by the linear expression of the distance;
calculating a normalized intensity distribution by normalizing the intensity distribution with the approximate intensity distribution; and
calculating the power coupling coefficient from the normalized intensity distribution.
2. The power coupling coefficient measurement method of claim 1 , wherein the calculating the power coupling coefficient includes calculating the power coupling coefficient using the equation:
h=− ¼ z*In (( P bs1 ( z )/ P conv ( z ))−1),
where h is the power coupling coefficient, In represents natural log, and P bs1 (z) is the normalized intensity distribution for the core to which the test light pulse is input and P conv (z) is the approximate intensity distribution.
3. The power coupling coefficient measurement method of claim 1 , wherein the calculating the power coupling coefficient includes calculating the power coupling coefficient using the equation:
h=− ¼ z*In (1−( P bs2 ( z )/ P conv ( z ))),
where h is the power coupling coefficient, In represents natural log, and P bs2 (z) is the normalized intensity distribution for any one of the other cores to which the test light pulse is not input and P conv (z) is the approximate intensity distribution.
4. The power coupling coefficient measurement method of claim 1 , wherein the arithmetic device calculates the power coupling coefficient by using the equation:
h=− ¼ z*In (1−( P bs2 ( z )/ P conv ( z ))),
where h is the power coupling coefficient, In represents natural log, and P bs2 (z) is the normalized intensity distribution for any one of the other cores to which the test light pulse is not input and P conv (z) is the approximate intensity distribution.
5. A power coupling coefficient measurement device connected to one end of a multi-core fiber and measuring a power coupling coefficient of the multi-core fiber, comprising:
a test light pulse generator configured to generate a test light pulse;
an input/output device configured to input the test light pulse generated by the test light pulse generator to any one of cores of the multi-core fiber and to output backscattered light of the core to which the test light pulse is input or any one of the other cores;
a measurement device configured to measure an intensity distribution of the backscattered light output by the input/output device with respect to a distance from the one end of the multi-core fiber; and
an arithmetic device configured to calculate a power coupling coefficient from the intensity distribution of the backscattered light measured by the measurement device,
wherein, the arithmetic device calculates the power coupling coefficient by:
representing the intensity distribution in a logarithm,
calculating an approximate intensity distribution of a linear expression with respect to the distance on the basis of the intensity of the backscattered light in a region where the logarithm of the intensity distribution can be approximated by the linear expression of the distance,
calculating a normalized intensity distribution by normalizing the intensity distribution with the approximate intensity distribution, and
calculating the power coupling coefficient from the normalized intensity distribution.
6. The power coupling coefficient measurement device of claim 5 , wherein the arithmetic device calculates the power coupling coefficient by using the equation:
h=− ¼ z*In (( P bs1 ( z )/ P conv ( z ))−1),
where h is the power coupling coefficient, In represents natural log, and P bs1 (z) is the normalized intensity distribution for the core to which the test light pulse is input and P conv (z) is the approximate intensity distribution.