  We propose a newly configured optical correlation-domain reflectometry (OCDR)
without the use of an electrical spectrum analyzer (ESA) for high-speed
distributed reflectivity measurement with an enhanced spatial resolution.
First, the operation of ESA-free OCDR is analyzed by numerical simulation, the
results of which show the potential of the configuration to perform distributed
reflectivity measurement with an improved spatial resolution. Subsequently, the
simulation results are verified by comparison experiments, where distributed
reflectivity measurements along a 32-m-long single-mode fiber joint with
multiple connectors are performed using both conventional (with averaging) and
ESA-free OCDR configurations (without averaging) at a repetition rate of 100
Hz. The widths of the reflectivity peaks experimentally obtained by the
conventional and ESA-free OCDR configurations are 22.9 cm and 7.0 cm,
respectively. Finally, we experimentally evaluated the performance of the
ESA-free OCDR at higher repetition rates, achieving 6.3-cm spatial resolution
at a repetition rate of 1 kHz. This result indicates that the ESA-free OCDR can
perform a distributed reflectivity measurement with an improved spatial
resolution at a higher operation speed than ever.
