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A bidirectional wavelength division multiplexing (WDM) analog radio-over-fiber (A-RoF) mobile fronthaul (MFH) link is enhanced using photonic integrated devices. Two key photonic integrated devices are combined in the A-RoF link: an 8-channel InP directly modulated laser (DML) transmitter and a 32×100-GHz silicon array waveguide grating (AWG). The DML transmitter has 8 parallel monolithically integrated distributed feedback lasers, enabling cooperative and reconfigurable downlink analog transmission. Moreover, the 32×100-GHz AWG is featured by low insertion loss (

For civil and military applications, the ability to instantaneously capture and process wideband RF (radio-frequency) signal is of great importance. In this paper, a novel photonics-assisted RF channelized receiver aiming for instantaneous broadband RF signal reception is proposed and experimentally demonstrated. The channelizer is composed of two branches. In one branch, an optical frequency comb (OFC) is generated through a phase modulator (PM), while in the other the optical carrier is frequency-shifted via a polarization modulator (PolM) and then modulated by the captured unknown RF signal. Next, the frequency information of the unknown signal is derived from the frequency sum and the power difference of two specific beating tones, while the incorporation of the comb spacing and the amplitude profile of the OFC enable resolving the ambiguity cases. In the experiments, four receiving channels are constructed using five selected comb lines. The reception and analysis of several RF signals including single-tone, multi-tone and linear frequency modulation (LFM) ones within 1-40 GHz are experimentally validated, which can be extended up to 72 GHz in theory. The proposed channelizer is characterized with ambiguous-free capability, low measurement errors less than 2 MHz, and an SFDR of ~92 dB·Hz2/3.

Microwave frequency downconversion is optically implemented by using two cascaded polarization modulators (PolMs), characterized by full-frequency-range coverage and high conversion efficiency. In this proposed approach, the incident radio-frequency signal (RF) and the local oscillator signal (LO) are applied to the first PolM at the transmitter and the second one at the receiver, respectively. Effective optical carrier suppression can be achieved using the cascaded PolMs, whereas the optical sidebands induced by the RF and the LO signals remain unchanged. Since no additional optical filter is needed, the lower operation frequency limit in other approaches with an optical filter is eliminated, such that a full-frequency-range coverage is ensured in this approach. Meanwhile, the use of optical carrier suppression (OCS) enables high conversion efficiency for microwave downconversion. In the proof-of-concept experiments, the conversion efficiency is improved by over 20 dB within the frequency range from 2 to 15 GHz, as compared to those of cascaded modulators without OCS. Both the upper and the lower limits of such a frequency range can be greatly extended when test instruments with full frequency range are used.

Due to the high energy efficiency per bit and high sensitivity, Return-to-zero differential-phase-shift-keying (RZ-DPSK) is perfectly suitable for free-space laser communications. However, the conventional generation method of RZ-DPSK optical signal requires two modulators, which is costly, bulky, and heavy, significantly hindering the application of RZ-DPSK in size, weight, and power (SWaP)-constrained satellite platforms. In this paper, we propose and experimentally demonstrate a modulator-free variable multi-rate RZ-DPSK free-space optical (FSO) communication system based on chirp-managed laser (CML). Based on the proposed scheme, an FSO outfield experiment over 1 km has been successfully undertaken, achieving receiving sensitivities of −48.9 dBm and −45.6 dBm at 2.5 Gbps and 5 Gbps, with bit error rate (BER) of 1 × 10−3 without forward error correction (FEC), respectively. The performance of the proposed system is also investigated by studying the eye diagrams under two different test conditions of back-to-back transmission and 1-km free space transmission. In addition to the small size, lightweight and low cost, the proposed scheme shows great potential for a variety of FSO communication applications ranging from Cube-Star to larger satellite laser communication platforms.