Qibing Wang

Experimental Layered/Enhanced ACO-OFDM Short-Haul Optical Fiber Link

Asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) is theoretically more optically power efficient than dc-biased OFDM (DCO-OFDM); unfortunately, its spectral efficiency is halved to accommodate the clipping distortion. Recently, layered/enhanced ACO-OFDM has been developed to mostly regain the lost spectral efficiency, and theoretically compared with other modulation formats. In this letter, we experimentally demonstrate L/E-ACO-OFDM for the first time over a fiber link. We transmit over a 19.8-km single mode fiber at 4.375 Gb/s, and show a 2-dB improvement in signal quality for the same laser bias current and received optical power over DCO-OFDM.

Hardware-efficient signal generation of layered/enhanced ACO-OFDM for short-haul fiber-optic links

Layered/enhanced ACO-OFDM is a promising candidate for intensity modulation and direct-detection based short-haul fiber-optic links due to its both power and spectral efficiency. In this paper, we firstly demonstrate a hardware-efficient real-time 9.375 Gb/s QPSK-encoded layered/enhanced asymmetrical clipped optical OFDM (L/E-ACO-OFDM) transmitter using a Virtex-6 FPGA. This L/E-ACO-OFDM signal is successfully transmitted over 20-km uncompensated standard single-mode fiber (S-SMF) using a directly modulated laser. Several methods are explored to reduce the FPGAs logic resource utilization by taking advantage of the L/E-ACO-OFDMs signal characteristics. We show that the logic resource occupation of L/E-ACO-OFDM transmitter is almost the same as that of DC-biased OFDM transmitter when they achieve the same spectral efficiency, proving its great potential to be used in a real-time short-haul optical transmission link.

Efficient IFFT implementation in an ACO-OFDM transmitter

A computationally efficient IFFT implementation for asymmetrically clipped optical OFDM transmitter is proposed and implemented in a Field-Programmable Gate Array. The overall computational complexity is reduced by 68% in a real-time transmitter.

Compact 4×5 Gb/s silicon-on-insulator OFDM transmitter

We characterize an integrated silicon 4×5 Gb/s OFDM transmitter PIC (2.1×4.8 mm²) with four modulators and an optical Fourier transform. This PIC features a channel spacing of 5 GHz and an 80-GHz free spectral range.

Real-Time Demonstration of Augmented-Spectral-Efficiency DMT Transmitter Using a Single IFFT

Increasing the power and spectral efficiency in intensity-modulated direct-detection short-haul fiber-optic links enables higher data rates in power- and bandwidth-limited optical communication systems. Augmented spectral efficiency discrete multi-tone (ASE-DMT) can improve the spectral efficiency of pulse-amplitude-modulated DMT while maintaining its power advantage over dc-biased DMT, whose transmitter requires only one inverse fast Fourier transform (IFFT) with Hermitian symmetric inputs. Although the ASE-DMT transmitter requires multiple IFFTs, we show how these can be mapped onto a single IFFT, by using both the real and imaginary outputs of the IFFT and by extracting some signals from within the IFFTs structure. Using only one IFFT, we first demonstrate a real-time PAM4-encoded optical ASE-DMT transmitter with a net data rate of 18.4 Gb/s. When implemented in a FPGA, using a single IFFT saves 30% of logic resources, compared with a four-IFFT ASE-DMT transmitter. Finally, a 1550-nm directly modulated laser is used to evaluate its optical transmission performance with offline signal processing in the receiver. Without using any optical amplifiers, the ASE-DMT signal can be successfully transmitted over 10-km standard single-mode fiber (SSMF), but fails over 20-km SSMF due to the influence of fiber dispersion and laser chirp.