High-speed high-resolution optical correlation-domain reflectometry without using electrical spectrum analyzer

Observation of Rayleigh scattering by simplified optical correlation-domain reflectometry without frequency shifter

“…[27][28][29] To further simplify the OCDR system, we have recently developed a new configuration that eliminates the need for an electrical spectrum analyzer (ESA), which builds upon the AOM-free OCDR system and boasts enhanced spatial resolution and operational speed. 30) However, these improvements come at a cost of significant noise for long-range measurements, as has been reported previously. 31) Note that the key difference between ESA-free OCDR and AOM-free OCDR is in their electrical signal processing, while their spatially resolving techniques are identical, resulting in the same measurement range in principle.…”

“…As an alternative to OTDR and OFDR, optical correlationdomain reflectometry (OCDR) [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] has been developed on the basis of the synthesis of optical coherence functions. 15) OCDR can be implemented at a relatively low cost and has a unique advantage called random accessibility, i.e.…”

Compensation of noise floor distortion in long-range simplified optical correlation-domain reflectometry without the use of electrical spectrum analyzer

“…Distributed reflectivity measurement was performed within a relatively short range on the FUT, achieving 6.3 cm spatial resolution at an operational speed of 1 kHz, which indicated the elimination of the trade-off relation between operation speed and spatial resolution in OCDR systems. 26) However, the simulation result revealed that the noise floor of the reflectivity distribution measured with the ESA-free OCDR is distorted, which deteriorates the measurement over long ranges. With subsequent experiments, the distortion was also verified to be growingly significant as the measurement range extended.…”

“…24) Another simplified configuration without the direct use of a reference path was also reported. 25) To further simplify the OCDR system, we proposed a newly configured OCDR without the use of an electrical spectrum analyzer (ESA) 26) on the basis of the AOM-free OCDR. Distributed reflectivity measurement was performed within a relatively short range on the FUT, achieving 6.3 cm spatial resolution at an operational speed of 1 kHz, which indicated the elimination of the trade-off relation between operation speed and spatial resolution in OCDR systems.…”

“…In the electrical system, the electrical beat signal of the incident and reference light is directly analyzed with the oscilloscope (OSC), in which its time-domain intensity is observed with the "peak detect" function. The intensity of the beat signal is given by 26) p t…”