PIERS ONLINE, VOL. 3, NO. 7, 2007 1071 Lightwave Technique of mm-Wave Generation for Broadband Mobile Communication B. N. Biswas 1 , A. Banerjee 1 , A. Mukherjee 1 , and S. Kar 2 1 Academy of Technology, Hooghly 712121, India 2 Institute of Radio Physics and Electronics, Kolkata 700009, India Abstract— In future generation pico-cellular mobile communications FM-sideband injection of two laser sources are used to generate mm-wave signals. This paper considers some over- looked issues with particular emphasis on the loss of coherence between the two lasers due to cycle slipping phenomenon and suggests a new tracking system, that considerably improves the performance. DOI: 10.2529/PIERS061004061503 1. INTRODUCTION Increasing demand for broadband mobile communication and limited atmospheric propagation at mm-waves has resulted in the need for high density of pico-cells. And as such future cellular broad- band mobile communication systems will comprise mm-wave components for radio link between the mobile station (MS) and the numerous base stations (BS), which are remotely controlled by the central station (CS). Moreover, the base stations are widely separated from the central station, optical transport of the mm-wave signal is the choice owing to the inherently low transmission loss coefficient of the optical fibers. This, in turn, requires the use of lasers and photo-detectors. The cost of numerous BS’s should be kept as low as possible. Therefore, generation and control of mm-wave signals should be optically carried out at the control station, making use of the proposed optical devices needed for the purpose of transport of the mm-wave signals. This avoids the need for mm-wave oscillators and modulators in the numerous base stations. In achieving this purpose two approaches are adopted, viz., (1) single optical source technique and (2) multiple optical source technique. In this we present a method based on multiple optical source technique using sideband separation principle. This is depicted in Fig. 1. Frequency Modualted Master Laser Isolater Slave Laser - I Slave Laser - II Photo Diode MW Signal Slave Laser - I Slave Laser - II Frequency Modulated Master Laser Figure 1: Coherent mixina of two optical sources. The single optical source technique is the simplest approach for impressing microwave signal on an optical carrier. It can be realized either by direct current modulation of semiconductor laser or with an electro-optic modulator (Mach Zehnder Modulator MZM). Direct current modulation