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A high resolution FMCW Lidar system based on a phase-diverse self-homodyne coherent receiver is demonstrated. Using the same linearly chirped waveform for both the transmitted lidar signal and the local oscillator, the self-homodyne coherent receiver performs frequency de-chirping in the photodiodes which significantly simplifies the task of signal processing, and the required receiver bandwidth can be much lower than the signal chirping bandwidth. While only amplitude modulation is required in the lidar transmitter, phase-diverse coherent receiver allows simultaneous detection of target range and velocity through the spectrum of the de-chirped complex waveform. Multi-target detection is also demonstrated experimentally.

 

Performance of distributed Raman amplification (DRA) system with dual order forward (FW) pumping is analyzed with the consideration of both pump relative intensity noise (RIN) to signal phase noise transfer and signal nonlinear interference. The efficiencies of pump RIN to signal phase noise transfer are theoretically analyzed and experimentally verified by measuring signal phase noise introduced by small index intensity modulations applied on the pump lasers. The results indicate that the efficiency of 2nd order pump RIN to signal phase noise transfer can be more than 2 orders of magnitude higher than that from the 1st order pump. Although dual order FW Raman pumping corresponds to a slight increase of amplified spontaneous emission (ASE) compared to using only a 1st order pump, its major advantage comes from the reduction of nonlinear interference noise in a dense wavelength-division multiplexing (DWDM) system. Because pump RIN to signal phase noise transfer has lowpass characteristics, systems at high baud rates, such as 100 Gbaud, are less susceptible to the impact of pump laser RIN. 

We demonstrate 20-channel coherent transmission using a high-power single-section QW FP-laser diode over 78.3 km single mode fiber. The system capability can reach > 4Tb/s with a single laser in the transmitter using polarizations multiplexing.

 

Electrostriction in an optical fiber is introduced by interaction between the forward propagated optical signal and the acoustic standing waves in the radial direction resonating between the center of the core and the cladding circumference of the fiber. The response of electrostriction is dependent on fiber parameters, especially the mode field radius. We demonstrated a novel technique that can be used to characterize fiber properties by means of measuring their electrostriction response under intensity modulation. As the spectral envelope of electrostriction-induced propagation loss is anti-symmetrical, the signal to noise ratio can be significantly increased by subtracting the measured spectrum from its complex conjugate. We show that if the transversal field distribution of the fiber propagation mode is Gaussian, the envelope of the electrostriction-induced loss spectrum closely follows a Maxwellian distribution whose shape can be specified by a single parameter determined by the mode field radius. 

We present a simple technique for in-field determination of fiber types through the measurement of electrostriction effect based on self-phase modulation 

We demonstrate a novel technique to measure the nonlinear phase shifts of multi-span fiber optic links with a polarization-multiplexed coherent transceiver based on cross-phase modulation between two orthogonally polarized subcarrier tones.