Multi-wavelength semiconductor laser arrays (MLAs) have wide applications in wavelength multiplexing division (WDM) networks. In spite of their tremendous potential, adoption of the MLA has been hampered by a number of issues, particularly wavelength precision and fabrication cost. In this paper, we report high channel count MLAs in which the wavelengths of each channel can be determined precisely through low-cost standard [mgr]m-level photolithography/holographic lithography and the reconstruction-equivalent-chirp (REC) technique. 60-wavelength MLAs with good wavelength spacing uniformity have been demonstrated experimentally, in which nearly 83% lasers are within a wavelength deviation of [plusmn]0.20[emsp14]nm, corresponding to a tolerance of [plusmn]0.032[emsp14]nm in the period pitch. As a result of employing the equivalent phase shift technique, the single longitudinal mode (SLM) yield is nearly 100%, while the theoretical yield of standard DFB lasers is only around 33.3%.

An eight-wavelength distributed feedback semiconductor laser array with $\lambda /4$ equivalent phase shift based on reconstruction-equivalent-chirp technique was demonstrated. It shows very good linearity in lasing wavelengths with its deviation from $-0.22$ to 0.20 nm. The threshold currents are between 19 and 24 mA. The side-mode suppression ratios are all larger than 40 dB under the bias currents of 70 mA. The slope efficiencies at room temperature are all about $0.4\mathrm{W}/\mathrm{A}$. The grating was fabricated only by common holographic exposure and an additional micrometer-level conventional photolithography, which results in a low cost.

A multilongitudinal mode fiber laser sensor formed by two fiber Bragg gratings and a piece of erbium-doped fiber is first proposed and validated experimentally. When the strain is applied on the sensor, the laser cavity is stretched, which leads to a change of round-trip frequency. Thus the strain can be obtained by measuring the beat frequency of the resonant cavity. The proposed sensor is found to be characterized with simplicity, easy setup, high resolution, low-cost demodulation, and good stability. Experimental results show that the sensor has a sensitivity of $-1.1\mathrm{KHz}∕\mu ϵ$ and the root-mean-square deviation of $3.6\mu ϵ$.

A unified data communication and radar sensing system towards millimeter-wave (mm-wave) applications with extended coverage is proposed and experimentally demonstrated. The transmission and reception of mm-wave signals are implemented by microwave photonics technologies, such as superheterodyne optical carrier suppression (HeteroOCS) and analog photonic links based on polarization modulators (PolMs). The orthogonal frequency division multiplexing (OFDM) signal is employed for communications and radar sensing simultaneously. The HeteroOCS is used to up-convert the intermediate frequency (IF) OFDM signal to the mm-wave band in the central office (CO). Then the optical mm-wave signal is transmitted to the remote antenna units (RAUs) via optical fibers. The echo signal is received by the RAU which is remotely connected to the CO by a PolM-based photonic link. The chromatic dispersion of optical fibers in the transmitter and receiver links is overcome by the HeteroOCS and the PolM, respectively. In the proposed system, the baseband units (BBU) centralized in the CO is used to process the radar sensing signal. As a result, the fiber length puts a restriction on the data rate of the communication. We propose a pre-delayed trigger signal to overcome the fiber length limitation. A proof-of-concept experiment is performed. Two targets with distances of 1.64 m and 3.40 m are successfully detected separately. The communication function of the system is also verified. 1 m wireless transmission of 1.56 Gb/s data rate is achieved below the forward error correction limit.

Multi-wavelength laser arrays (MLAs) with a high wavelength-spacing precision are designed and fabricated. The MLAs are realized by the reconstruction-equivalent chirp (REC) technique, and anti-reflection structures are used to decrease the wavelength deviation. Six multi-wavelength laser arrays are fabricated and tested. Statistical results show that 81.1% of all 95 lasers have wavelength deviations within $\pm 0.1\mathrm{nm}$, and all of them are within $\pm 0.2\mathrm{nm}$. The mean wavelength spacing is 1.605 nm, and the standard deviation is 0.132 nm.

Hybrid free space optical (FSO)/radio frequency (RF) systems have been proved to be reliable links for high-data-rate wireless backhauls. In this paper, we present a unified performance analysis of the hybrid FSO/RF transmission system which transmits the identical data in both links and implements two popular diversity combining schemes, namely, selection combining (SC) and maximal ratio combining (MRC), in the receiver. Specially, for the FSO link, the Gamma-Gamma turbulence with pointing errors under heterodyne detection (HD) and intensity modulation/direction detection (IM/DD) is considered in our analysis while the general - shadowed fading which unifies popular RF fading models is employed for the analysis of the RF link. As a result, unified closed-form expressions of outage probabilities and average bit error rates for different modulation schemes are derived. Analytical and Monte Carlo simulation results are provided to characterize the performance of the hybrid FSO/RF link which is compared to the single FSO link and the single RF link. The agreement between the analytical and simulation results confirms the unification of various FSO channels and RF fading scenarios into a single closed-form expression.