Jiaxiong Li

Improving the Spatial Resolution of an OFDR Based on Recirculating Frequency Shifter

We demonstrate a novel method for obtaining high spatial resolution optical frequency domain reflectometry (OFDR) utilizing recirculating frequency shifter for broadening the optical frequency sweeping. Twelve times broadened optical frequency sweeping is achieved. We obtain 0.97 cm spatial resolution over 710-m measurement range with modulation frequency sweeping span of 882 MHz. Such a spatial resolution corresponds to a frequency sweeping span of 10.31 GHz. The experimental results indicate that the measurement range can be extended to 10 km, based on the proposed method.

Second-order few-mode Raman amplifier for mode-division multiplexed optical communication systems.

We experimentally demonstrate and investigate, for first time to our best knowledge, a second-order few-mode Raman amplifier for low noise distributed fiber amplification. The 1455 and 1360 nm pumps are both injected into the few-mode fiber (FMF) in the forms of two degenerate LP11 modes in the backward direction. Within the band from 1542 to 1558 nm, maximum on-off gains of 4 dB are achieved for both LP01 and LP11 modes, and the differential modal gain (DMG) is less than 0.4 dB. The noise figure (NF) improvements at 1550 nm for LP01 and LP11 modes are 1.2 dB and 1.1 dB, respectively, compared with the conventional first-order pumping scheme. The lowest NFs of less than -2 dB are achieved for both modes. We build an optical time-domain reflectometer (OTDR) in the few-mode distributed Raman amplifier (FM-DRA) to measure the signal evolutions, and the results indicate a proof-of-concept low noise amplification for second-order pumping with respect to the conventional first-order pumping case. Due to the second-order pumping, broadened Raman amplification band has been observed with improved gain flatness for both LP01 and LP11 modes, which is also of great importance in the optical communication systems. The second-order FM-DRA can be used potentially in future high capacity mode-division multiplexing (MDM) optical communication systems.

Broadened optical frequency sweeping for high spatial resolution OFDR based on recirculating frequency shifter

We demonstrate a novel method for obtaining high spatial resolution optical frequency domain reflectometry (OFDR) utilizing recirculating frequency shifter for broadening the optical frequency sweeping. 10-times broadened optical frequency sweeping is achieved. 1.46-cm spatial resolution is obtained with modulation frequency sweeping span of 712 MHz.

Orientation-insensitive mode-selective coupler for two-mode transmission at 850 nm using standard SMF

We demonstrate the design of an orientation-insensitive mode-selective coupler working as a DeMUX for two-mode transmission at 850 nm using SSMF. The mode extinction ratios of LP01/LP11 and LP11/LP01 are above 12.6 dB and 21.2 dB in the band of 845 to 855 nm.