Frequency Multiplication Millimeter-Wave Generated by Polarization Modulator with Inserting Pilot and Transmitted Over Fiber Without Bit Walk-Off Effect.

A novel inserting pilot radio over fiber (ROF) system to generate and distribute a frequency quadrupling/12-tupling millimeter wave (MMW) without the bit walk-off effect by two parallel polarization modulators (DP-PolM) is proposed. For our proposed system, the operation principle is analyzed, the simulation link is built and the feasibility is verified. In the back-to-back system, by properly adjusting the modulation index of the DP-PolMs, the phase shift of the phase shifter (EPS) and the polarization angle of the polarizer, the main component of the output signal from the DP-PolMs includes ±2th-/±6th-order sidebands. In the data transmission system, the data signal is first split into two beams, one of which modulates the RF drive signal with an electrical phase modulator (PM), the other is amplified by an electrical gainer (EG) first, and then the two beams' data signals are combined into one and used as the composite RF drive signal of the DP-PolM. By adjusting the modulation index of the PM and the gain of the EG, the data signal can be modulated only on the +2th-/+6th-order optical sideband of the output signal from the DP-PolM. The optical carrier from the laser is split into two branches, one of which is sent into the DP-PolM, and the other is used as a pilot signal. The output signals of DP-PolM and the pilot signal are combined and transmitted to the base station (BS) via optical fiber. At the BS, the pilot signal is filtered out by a fiber Bragg grating (FBG) and used as the carrier for the uplink for carrier reuse. The output signal from the FBG is injected into the photodetector, and the frequency quadrupling/12-tupling MMW with downlink data is generated. The influence of the key parameters diverging from their theoretical and adult values on the bit error rate (BER) and Q factors is also analyzed. Our scheme can not only effectively overcome the bit walk-off effect caused by optical fiber chromatic dispersion and greatly increase the fiber transmission distance, but also can effectively improve the performance of the uplink and downlink of the system by using a pilot signal as the uplink optical carrier. Our proposed scheme has important application prospects in the MM ROF system. We have designed a frequency 4/12 tupling MMW ROF system by PoIM. By loading the composite RF drive signal on the PoIM, the downlink data signal is modulated only to the +2/+6th order sidebands, which overcomes the bit walk-off effect and increases the transmission distance. By separating part of the optical carrier as the pilot in the CS, and in the BS, the pilot is filtered out and used as the uplink carrier, which increases the downlink performance and the tunability of the system. [ABSTRACT FROM AUTHOR]