Design and analysis of all optical RF transceiver using polarization modulators

Abstract

All optical multiband radio transceiver is designed using Polarization Modulators. Polarization Modulators have been gaining popularity in recent times as the device is free from bias drift problem that is commonly noticed in Mach Zhender intensity modulator. Two continuous wave (CW) optical frequencies separated by 26.25 GHz are selected from optical frequency comb generator designed using two parallel polarization modulators. Two subcarrier multiplexed (SCM) signal is modulated on a comb frequency using a polarization modulator. The SCM modulated optical signal and another CW optical comb separated by 26.25 GHz are fed to a remote radio access unit (RAU) via a single mode fibre. The two signals are heterodyned in a photo detector at a remote RAU producing multi radios at 27.25 GHz and 28.75 GHz in 5G New Radio frequency band of n258 (24.25–27.5 GHz) and n257 (26.5–29.5 GHz). In the receiver part of the transceiver, the received 5G signals are modulated by a Polarization Modulator with a CW optical comb frequency and the resultant optical sidebands along with the carrier are fed to the baseband unit (BBU) at the central office via a return fiber. At the BBU the signals are heterodyned in a photo-detector with a CW comb frequency to produce the down converted baseband output at the BBU. The proposed transceiver scheme is analysed and simulation is carried out inOptisystem16® platform. BER performance of the received signal with various laser powers show that the scheme is practically implementable. In particular BER of 10−6 is obtained at the photodetector output in the transmitted (downlink) signal and returned link (uplink) signal at 2.25 dBm laser power. Two tone IMD analysis of the transmitted signal provides input and output third order intercept point at 52 dBm and 32 dBm respectively. Spurious free dynamic range (SFDR) between fundamental and 3rd order intermodulation distortion product obtained is 85 dB.Hz2/3 considering a noise floor of − 140 dBc/Hz.