Yufeng Shao

A Novel Radio-Over-Fiber System With Wavelength Reuse for Upstream Data Connection

We have experimentally demonstrated a novel wavelength reuse scheme for up-link connection in a radio-over-fiber (ROF) system. The dual-mode lightwave generated by optical carrier suppression modulation is separated by an optical interleaver. One of the dual-mode lightwaves is modulated with a baseband data at 2.5 Gb/s. The other lightwave will be used for the optical carrier for the up-link data modulation. There is no additional laser source for the upstream data generation in the base station. By this method, we simplify the configuration of the ROF system and reduce the cost of the system

Observation of central wavelength dynamics in erbium-doped fiber ring laser.

We report on the observation of central wavelength dynamics in an erbium-doped fiber ring laser by using the nonlinear polarization rotating technique. The evolution of central wavelength with the laser operation state was observed experimentally. Numerical simulations confirmed the experimental observation and further demonstrated that the dynamics of wavelength evolution is due to the combined effects of fiber birefringence, fiber nonlinearity, and cavity filter.

A staggered differential phase-shift keying modulation format for 100Gbit/s applications

We propose and demonstrate by numerical simulation a new phase modulation format, the staggered differential phase-shift keying (SDPSK), for 100 Gbit/s applications. Non-return-to-zero (NRZ) SDPSK signals was generated by using two phase modulators, and return-to-zero (RZ) SDPSK signals with 50% duty cycle was generated by cascading a dual-arm Mach-Zehnder modulator. The demodulation of 2 bit/symbol can be simply achieved on 1 bit rate through only one Mach-Zehnder delay interferometer and a balanced receiver. By comparing the transmission characteristics of the two staggered phase modulation formats with those of NRZ-DPSK, RZ-DPSK, NRZ-DQPSK, and RZ-DQPSK, respectively, we show that, the SDPSK signal has similar chromatic dispersion and polarization-mode-dispersion tolerance to the DPSK signal with same NRZ or RZ shape, while the SDPSK signal has stronger nonlinear tolerance than the DPSK or DQPSK signal. In addition, the SDPSK signal has the best transmission performance when each signal was transmitted over 106km optical SMF+DCF, and then launched into a third-order Gaussian optical bandpass filter placed with beyond 125GHz bandwidth.

Duobinary RZ and Dark RZ signals generation using only one differential Mach-Zehnder modulator

We propose a novel scheme to generate duobinary RZ and dark RZ signals. It needs only one differential Mach-Zehnder modulator (DMZM), which can adjust the operating point of the modulator to generate duobinary RZ and dark RZ signals easily. It is more cost-effective compared to conventional schemes due to its simple configuration.

A Novel Scheme to Generate Orthogonal Modulation Label Based on DPSK Payload and Duobinary RZ Label

A novel scheme to generate orthogonal modulation label based on differential phase-shift keying (DPSK) payload and duobinary RZ label has been proposed. The duobinary RZ label with tunable pulse-width and extinction ratio is generated by using a differential Mach-Zehnder modulator (DMZM). Our numerical simulation results have shown that both DPSK payload and duobinary RZ label have large receiver power margin.

Modified duobinary signals with tunable duty cycle and its application in a label switching optical network

A novel configuration to use modified duobinary signals with tunable duty cycle as optical labels in optical packet switching system is proposed. The performance of 10 Gbit/s DPSK payload with 2.5 Gbit/s MD-RZ label is analysed.

Encoding and transmission of orthogonally optical label switching using DQPSK payload and MD-RZ label

Optical label switching (OLS) has been regarded as an efficient technique to route and forward IP packets transparently in the optical layer. In label switching system, orthogonal modulation has shown some advantages, such as its high spectral efficiency. One example is the combination of amplitude-shift-keying (ASK) label and differential phase-shift-keying (DPSK) payload. However, differential quadrature phase-shift-keying (DQPSK) payload has not been used in optical label switching system yet. In this letter, we propose and demonstrate a novel optical label switching scheme by the combination modified return zero (MD-RZ) and DQPSK for the first time. The transmitter is set up by cascading two phase modulators (PM) and one dual-arm LiNbO3 modulator (LN-MOD). The signal is first phase modulated by two PMs. The MD-RZ label is then impressed by the subsequent LN-MOD. Duty cycle and extinction ratio of the MD-RZ labels are tunable. The DQPSK payload can be used in a 20Gbit/s optical label switching system, with 2-bit per symbol modulation/demodulation. Within the network, the label information is read, processed and updated, a process known as label switching, until the burst reaches the desired egress edge node. The use of balanced detection is expected to improve performance for the payload. The transmission performance of 20Gbit/s DQPSK payload with 2.5Gb/s MD-RZ-ASK label is also analysed. MD-RZ labeling of a DQPSK payload has been shown to be a promising candidate for the implementation of OLS system.

A novel scheme to generate optical dark RZ pulse and its applications in an orthogonal modulation system

A configuration of transmitter for superimposing DPSK signals on dark RZ signals with tunable duty cycle was proposed. The transmitter comprises two optical phase modulators and a delayed line Mach-Zehnder interferometer. The simulation results show that the spectral efficiency is doubled by using this scheme.