Electric field distribution fluctuation period measuring method and electric field distribution fluctuation period measuring device
An electric field distribution variation cycle measuring apparatus and method involve measuring or estimating a variation cycle of an electric field distribution in an optical fiber. Pump light and probe light may be converted into a higher-order mode and cause the pump light to be incident on while end of the optical fiber and probe light to be incident on the other end of the optical fiber. A Brillouin gain of simulated Brillouin scattering may be acquired, where the stimulated Brillouin scattering is generated when the pump light and the probe light collide in the optical fiber. A variation cycle of the Brillouin gain may be set as a variation cycle of an electric field distribution of a higher-order mode.
1 . An electric field distribution variation cycle measuring method for measuring a variation cycle of an overlap of an electric field distribution between first and second higher-order modes propagating through an optical fiber, the electric field distribution variation cycle measuring method comprising:
converting pump light into the first higher-order mode and converting probe light having a predetermined optical frequency difference from the pump light into the second higher-order mode;
causing the pump light to be incident on one end of the optical fiber and the probe light to be incident on the other end of the optical fiber;
receiving, at the one of the optical fiber, the probe light in the state of the second higher-order mode after passing through the optical fiber and including a stimulated Brillouin scattering generated when the pump light and the probe light collide in the optical fiber in a distributed manner in a longitudinal direction of the optical fiber;
acquiring a Brillouin gain of a desired acoustic wave mode of the stimulated Brillouin scattering; and
setting a variation cycle of the Brillouin gain in the longitudinal direction of the optical fiber as the variation cycle of the overlap of the electric field distribution between the first and second higher-order modes.
2 . The electric field distribution variation cycle measuring method according to claim 1 , wherein the desired acoustic wave mode is a fundamental mode.
3 . An electric field distribution variation cycle measuring apparatus that measures a variation cycle of an overlap of an electric field distribution between first and second higher-order modes propagating through an optical fiber, the electric field distribution variation cycle measuring apparatus comprising:
a mode multiplexing and demultiplexing device that converts pump light into the first higher-order mode and converts probe light having a predetermined optical frequency difference from the pump light into the second higher-order mode and causes the pump light to be incident on one end of the optical fiber and the probe light to be incident on the other end of the optical fiber; and
a gain analysis device that receives, at one end of the optical fiber, the probe light in the state of the second higher-order mode after passing through the optical fiber and including a stimulated Brillouin scattering generated when the pump light and the probe light collide in the optical fiber in a distributed manner in a longitudinal direction of the optical fiber, acquires a Brillouin gain of a desired wave mode of the stimulated Brillouin scattering, and sets a variation cycle of the Brillouin gain in the longitudinal direction of the optical fiber as the variation cycle of the overlap of the electric field distribution between the first and second higher-order modes.
4 . The electric field distribution variation cycle measuring apparatus according to claim 3 , wherein the desired wave mode is a fundamental mode.