Search

A radio-on-fiber system is proposed that uses a frequency-multiplexing technique to reduce the relative intensity noise (RIN) caused by reflections at optical fiber connectors. It is based on the simultaneous transmission of IF and local oscillation (LO) frequency. Optimum LO frequency and optical modulation index that minimize RIN are investigated by experiments and calculations assuming the double and multiple reflection situations. The results agree well and RIN reduction of 17 dB is obtained in multiple reflection situations. Index Terms--Microwave photonics, optical fiber connecting, optical noise, radio-on-fiber (ROF) system.

A predistortion-type equi-path linearizer is created for a radio-on-fiber system based on wide-band code division multiple access: its main benefit is its simple optical circuit configuration. Experiments show that the phase difference between the carrier and third-order intermodulation (IM3) component of the laser diodes (LDs) is shifted by around 90[degrees] from that of the RF amplifier. To our knowledge, this is the first report to describe this phase shift, which is observed with both Fabry-Perot and distributed-feedback LDs. To counter this shift, we use additional phase shifters. The proposed design places a pre-amplifier between the linearizer and LD for lower power consumption and better insertion gain at the linearizer. Experimental and calculated results agree well, and more than 20-dB improvement in the IM3 components is obtained over the bandwidth of 60 MHz. The linearizer works well in the temperature range of 10 [degrees]C to 40 [degrees]C with a simple control circuit. Index Terms--Linearization, microwave photonics, predistortion, radio-on-fiber (ROF) system, semiconductor lasers.

Single-pole double-throw switches composed of p-i-n diodes are proposed for multiband operations. A ladder resonance circuit is introduced to simplify their configuration and to reduce the cost. The isolation greater than 20 dB and the insertion loss less than 2 dB are achieved in experiments at three frequency bands: 1.6, 2.5, and 5.8 GHz. Resonance frequency variations are investigated in detail for two types of switches consisting of: 1) lumped circuit elements and 2) semimicrostrip elements. The variations on the semimicrostrip configuration are about 25 % of those with lumped circuit elements. The proposed switch does not influence the switching speed and signal distortion characteristics. It also showed good temperature stability from -30 °C to 485 °C. [ABSTRACT FROM AUTHOR]