We have experimentally compared the performances of optical millimeter-wave generation or up-conversion using external modulators based on different modulation schemes. The generated or up-converted optical millimeter wave using the optical carrier suppression (OCS) modulation scheme shows the highest receiver sensitivity, highest spectral efficiency, and smallest power penalty over long-distance delivery. Moreover, the OCS modulation scheme has a simple configuration and low-frequency bandwidth requirement for both electrical and optical components. Employing an OCS modulation scheme, 16-channel dense wavelength-division multiplexing signals at 2.5-Gb/s per channel have been up-converted to a 40-GHz carrier simultaneously.

Optical millimeter-wave generation or up-conversion using external modulators

The integration of optical and wireless systems is considered to be one of the most promising solutions for increasing the existing capacity and mobility as well as decreasing the costs in next-generation optical access networks. In this paper, several key enabling technologies for hybrid optical-wireless access networks are described, including optical millimeter-wave (mm-wave) generation, upconversion, and transmission in a downlink direction, and full-duplex operation based on wavelength reuse by using a centralized light source in an uplink direction. By employing these enabling technologies, we design and experimentally demonstrate an optical-wireless testbed that is simultaneously delivering wired and wireless services in the integrated optical-wireless and wavelength-division-multiplexing passive-optical-network access networks. The actual applications consisting of 270-Mb/s uncompressed standard-definition TV signal and 2.5-Gb/s data channels for downstream are successfully transmitted over a 25-km fiber and a 10.2-m indoor wireless link with less than a 1.5-dB power penalty. The results show that this integrated system is a practical solution to deliver superbroadband information services to both stationary and mobile users.

Key Enabling Technologies for Optical–Wireless Networks: Optical Millimeter-Wave Generation, Wavelength Reuse, and Architecture

We have experimentally demonstrated a full-duplex radio-over-fiber system using a single light source at central station (CS). Optical carrier suppression modulation scheme was employed to generate 40-GHz optical millimeter wave and up-convert the baseband signal simultaneously at CS for downlink transmission while the same optical carrier was reused at base station for uplink connection. The bidirectional full-duplex 2.5-Gb/s data was successfully transmitted over 40-km standard single-mode fiber (SMF-28) for both upstream and downstream channels with less than 2-dB power penalty. This system shows simple cost-efficient configuration and good performance over long-distance delivery

A full-duplex radio-over-fiber system based on optical carrier suppression and reuse

We have theoretically investigated the transmission performance of the optical millimeter-waves (mm-waves) generated using intensity modulation via a Mach-Zehnder modulator, with the double and single sidebands (DSB and SSB) and optical carrier suppression (OCS) schemes. According to our theoretical analysis, fiber chromatic dispersion leads to fading effect and time shifting of the codes; therefore, signals are greatly degraded. Of all signals, DSB optical mm-wave suffers from both the fading effect and the time shifting of the codes. However, the optical mm-waves generated by SSB and OCS schemes are immune to the fading effect, while the time shifting of the codes limits their transmission distance. Experimental and simulation results confirm the theoretical analysis.

Fiber Dispersion Influence on Transmission of the Optical Millimeter-Waves Generated Using LN-MZM Intensity Modulation

We proposed and experimentally demonstrated a novel scheme to generate an optical millimeter-wave and realized wavelength reuse for uplink connection in a radio-over-fiber system. We employed an optical interleaver to separate the spectrum of the double-sideband signals generated by a single-arm intensity external modulator. The separated first-order sideband modes were used to generate optical millimeter-wave with double RF frequency, while the separated optical carrier was reused for uplink connection

A Radio-Over-Fiber System With a Novel Scheme for Millimeter-Wave Generation and Wavelength Reuse for Up-Link Connection

We experimentally demonstrate the seamless integration of an 8/spl times/2.5 Gb/s wavelength-division-multiplexing passive optical network and radio-over-fiber access system using all-optical up-conversion based on Raman-assisted four-wave mixing in a high-nonlinear fiber. Dispersion-limited reach is extended to >20 km through vestigial-sideband filtering.

Jinxing Gu

Papers

Seamless integration of an 8/spl times/2.5 Gb/s WDM-PON and radio-over-fiber using all-optical up-conversion based on Raman-assisted FWM