Liquid crystal based active wavelength filter for phase-sensitive optical time domain reflectometry.

This study proposes a liquid-crystal-based active wavelength filter for phase-sensitive optical time domain reflectometry to mitigate the amplified spontaneous emission (ASE) noise and accurately match the passband with the light source. The validity of the proposed system was verified using comparative experiments with conventional passive optical filters. The experiment showed an increase in signal-to-noise ratio (SNR) of up to 2.21 dB compared with passive filters. Additionally, the proposed system can effectively eliminate ASE noise, resulting in an SNR of 12.99 dB.

Congestion estimation technique in the optical network unit registration process.

We present a congestion estimation technique (CET) to estimate the optical network unit (ONU) registration success ratio for the ONU registration process in passive optical networks. An optical line terminal (OLT) estimates the number of collided ONUs via the proposed scheme during the serial number state. The OLT can obtain congestion level among ONUs to be registered such that this information may be exploited to change the size of a quiet window to decrease the collision probability. We verified the efficiency of the proposed method through simulation and experimental results.

Dual cyclic power saving technique for XG-PON.

In a passive optical network (PON), energy conservation is an important system design goal to satisfy the global demands for an energy efficient green network. In this paper, we show that a separate period control for the transmitter and receiver of an optical transceiver can result in better power saving performances in PON systems. Then, we propose a power saving mode called the Dual Cyclic Sleep (DCS) mode. We have implemented the DCS mode in an ETRI XG-PON system and conducted experiments to show the power saving efficiency of the proposed DCS mode. The results indicate that the DCS mode provides higher power saving efficiency than the doze and cyclic sleep modes.

Optical burst add-drop multiplexing technique for sub-wavelength granularity in wavelength multiplexed ring networks.

We demonstrate optical burst add-drop multiplexing as a practical application of the optical burst switching technology in a wavelength-division-multiplexed ring network. To control optical bursts in the network, a burst identifier (BI) for delivering control information, and a BI processor for handling the BI, were designed. Optical bursts of 10- to 100-mus in length were optically multiplexed or demultiplexed in an intermediate node of the ring network. The demonstration shows that the optical burst add-drop multiplexing technique provides sub-wavelength granularity to a ring network.

All-optical flip-flop based on the bistability of injection locked Fabry-Perot laser diode.

We demonstrate the operation of a novel all-optical flip-flop. The flip-flop consists of a slave Fabry-Perot laser diode (FP-LD) and a specially designed master FP-LD which has a built-in external cavity and operates in single longitudinal mode oscillation. The set and reset pulses were generated by external modulators at 1 Gbit/s. The rising and falling times of the output signal in on-off operation of the flip-flop were about 50 ps. The required powers of both set and reset pulses were less than -9 dBm.