All-Optical Demultiplexing of WLAN and Cellular CDMA Radio Signals

Subcarrier multiplexed transmission of multimedia radio signals over fiber is often done to deliver broadband services cost effectively. These signals need to be demultiplexed, preferably in the optical domain, to avoid loss and noise due to optical-to-electrical conversion. However, it is challenging to optically isolate signals at subgigahertz range due to the need for very narrow optical bandpass filters with high selectivity and low insertion loss and distortion. We developed such a novel subpicometer all-optical bandpass filter by creating a resonance cavity using two closely matched fiber Bragg gratings. This filter has a bandwidth of 120 MHz at -3 dB, 360 MHz at -10 dB, and 1.5 GHz at -20 dB. Experimental results show that this filter optically separates two RF signals spaced as close as 50 MHz without significant distortion. This paper analytically and experimentally investigates the scenario when this filter was used with 2.4-GHz (wireless local area network) and 900-MHz (cellular wireless) radio signals. The bit-error rate of the underlying baseband data is related to the linearity and isolation of the filter.

[1]  M. Teich,et al.  Fundamentals of Photonics , 1991 .

[2]  P. A. Davies,et al.  Optical prefiltering in subcarrier systems , 1992 .

[3]  Marc Douay,et al.  Free spectral range variations of grating-based Fabry–Perot filters photowritten in optical fibers , 1995 .

[4]  Phil A. Davies,et al.  Optical demultiplexing for subcarrier multiplexed systems , 1995 .

[5]  Jeffrey H. Reed,et al.  A dynamic range enhancement technique for fiber optic microcell radio systems , 1995, 1995 IEEE 45th Vehicular Technology Conference. Countdown to the Wireless Twenty-First Century.

[6]  P. Ferdinand,et al.  Analysis of phase-shifted fiber Bragg gratings written with phase plates. , 1999, Applied optics.

[7]  N. Olsson,et al.  Erbium-Doped Fiber Amplifiers: Fundamentals and Technology , 1999 .

[8]  José Capmany,et al.  Experimental demonstration of optical prefiltering in WDM-SCM optical networks employing ultraselective optical bandpass filter , 1999 .

[9]  C. Roychoudhuri,et al.  Design of high finesse, wideband Fabry-Perot filter based on chirped fiber Bragg grating by numerical method , 2000 .

[10]  R. Hui,et al.  Subcarrier multiplexing for high-speed optical transmission , 2002 .

[11]  Hamed S. Al-Raweshidy,et al.  Radio Over Fiber Technologies for Mobile Communications Networks , 2002 .

[12]  Xavier Fernando,et al.  Optical domain demultiplexing of subcarrier multiplexed cellular and wireless LAN radio signals , 2005, Photonics North.

[13]  A. Nirmalathas,et al.  Transmission improvement in fiber wireless links using fiber Bragg gratings , 2005, IEEE Photonics Technology Letters.

[14]  Xavier N. Fernando,et al.  Analysis of Sub-Carrier Multiplexed Radio Over Fiber Link for the Simultaneous Support of WLAN and WCDMA Systems , 2005, Wirel. Pers. Commun..