Simplified optical correlation-domain reflectometry without reference path

Abstract

We develop a simplified configuration for optical correlation-domain reflectometry (OCDR) without an explicit reference path. Instead, the Fresnel-reflected light generated at the distal open end of the sensing fiber is exploited as a reference light. After the fundamental demonstration, the optimal incident power is found to be approximately 8 dBm. We also show that the loss near the distal end should not be applied, unlike in the case of Brillouin-based OCDR.

First demonstration of Brillouin optical correlation-domain reflectometry based on external modulation scheme

“…These drawbacks are also found in optical correlationdomain reflectometry (OCDR), [18][19][20][21][22][23] which is a Fresnelreflection-based technique for detecting low-quality connections, splices, and damaged parts along an optical fiber. We have developed a new OCDR configuration based on an external modulation scheme, in which, instead of directly modulating the driving current of a laser, the optical frequency is modulated using an electro-optic modulator (EOM).…”

External Modulation Optical Coherent Domain Reflectometry with Long Measurement Range

“…Optical reflectometry technologies, including optical time domain reflectometry (OTDR) [ 1 , 2 , 3 , 4 ], optical frequency domain reflectometry (OFDR) [ 5 , 6 , 7 , 8 , 9 ], and optical coherent domain reflectometry (OCDR) [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ], have been widely used in the monitoring of fiber link and distributed sensing applications. The OTDR simply measures the round-trip time of reflection and Rayleigh backscattering (RBS) of the probe pulse.…”

“…Here we focus on SOCF–OCDR, in which a high-order coherent spot is adopted for sensing, and the accessing position is controlled via a modulation parameter. To simplify the configuration, the reference arm can be replaced by the Fresnel-reflected light of the FUT [ 17 ], or the optical frequency shifter can be removed [ 18 ]. An external modulation scheme using an electro-optic modulator (EOM) was also adopted to overcome the issues caused by internal modulation [ 19 ].…”

Proposal of external modulation scheme for fiber-optic correlation-domain distributed sensing

“…The optical parts after dividing the laser output into two beams are basically the same as those of the direct modulation scheme. [21][22][23][24][25] In the external modulation scheme, instead of directly modulating the laser driving current, a double-sideband modulator (DSBM) and an optical band-pass filter are employed to modulate the optical frequency. The optical frequency shift corresponds to the frequency of the microwave applied from a voltage-controlled oscillator (VCO) to the DSBM.…”