A mobile broad-band communication system based on mode-locked lasers

Abstract

A concept is proposed for a pico-cellular network for broad-band mobile communication on a millimeter-wave basis. How microwave optical-signal-processing techniques based on mode-locked lasers (MLL's), optical modulators, and high-speed photo diodes (PD's) can advantageously be applied in the optical feeder lines of a pico-cellular network at 60 GHz is investigated. The external cavity MLL (at 81.25 GHz) used for the experiments showed an single-sideband (SSB) phase noise of 059 dBc/Hz at 100-Hz offset, when actively locked at 6.25 GHz. With the PD, and limited by the V -band mixer equipment, spectral harmonics up to 100 GHz could be detected. For the downlink configuration, a 400-MHz subcarrier is modulated with a 155-Mb/s data signal and upconverted to 62.9 GHz using an MLL and a fast PD. The upconverted sideband at 62.9 GHz was received with an optical power of 014.3-dBm at a bit-error-rate (BER) equal to 10 09 without any additional penalty due to transmitting the signal over 3 km of optical fiber. BER measurements at 155 Mb/s down to 10 011 were made. For the uplink, the digitally encoded RF signal is downconverted also by optical microwave signal processing. A 155-Mb/s data encoded 19.21-GHz signal is downconverted to 460 MHz using a mode-locked laser, an optical modulator, and a 600-MHz optical receiver front end. A receiver sensitivity of 024.5 dBm (BER equal to 10 09 ) is demonstrated with the microwave signal being transmitted over a 1-m radio link and 3 km of optical fiber.Index Terms-Fiber optics, mobile networks, optical communication, optical microwave, radio in the local loop.

Optical millimeter-wave generation and wireless data transmission using a dual-mode laser

“…Applying these methods millimeter-wave signals with excellent properties are obtained, however, these methods are comparatively complex. In the other case the optical waves to be heterodyned originate from a single laser using configurations like special external modulation schemes [6], [7], or by modelocked lasers [8], [9]. Very simple approaches with high spectral efficiency are dual-mode lasers, e.g., [10] and [11].…”

Design and demonstration of hardware efficient OPLL for generation of stable microwave signals by optical heterodyning

“…The optical signals for heterodyning can be derived from two independent lasers [1,2] or from one laser using the modulation-sideband technique [3] or dual mode laser [4]. Optical heterodyning using harmonic up-conversion in nonlinear lasers [5], mode-locked lasers and pulsed lasers [6] have also been reported. However, issues such as frequency instability and poor phase noise are inherent to optical heterodyning based approach for generation of microwave signals.…”