Showing papers by "Finisar published in 2021"

Frequency-Modulated Chirp Signals for Single-Photodiode Based Coherent LiDAR System

Abstract: In this paper, we investigate two categories of linear frequency-modulated chirp signals suitable for single-photodiode based coherent light detection and ranging (LiDAR) systems, namely, the frequency-modulated continuous-wave (FMCW) single-sideband (SSB) signal and the amplitude-modulated double-sideband (DSB) signal, and compare their achievable receiver sensitivity performance. The DSB signal requires a simpler transmitter design, as it is real-valued and can be generated using a single-drive Mach-Zehnder modulator (MZM), while the SSB signal, which is frequency/phase modulated, requires an in-phase and quadrature modulator (IQM)-based transmitter. A theoretical analysis of direct-detection (DD) beating interference (BI) especially the local oscillator (LO) beating with itself, known as LO-LO BI, is presented. Both Monte Carlo simulations and experimental demonstrations are carried out. Good agreement between simulations and experiments is achieved. In comparison with the SSB system, the DSB signal-based system is affected by laser phase noise-induced power fluctuation, and also suffers a significant sensitivity penalty due to nonlinear LO-LO BI. A spectral guard band for mitigating LO-LO BI is necessary for the DSB signal, achieved at the expense of requiring a larger electrical bandwidth. In system tests with a delay line of 385 m, the SSB signal outperforms the DSB signal with a 10 dB better receiver sensitivity in the case with a guard band, and 25 dB better sensitivity without a guard band.

Synthesis of SSB Nyquist 16QAM From Twin-SSB QPSK Via Optical Subcarrier Processing-Based Data Aggregation and its Direct Detection With Hierarchical Blind Phase Search Algorithm

Abstract: To synthesize a single-sideband (SSB) Nyquist high-order QAM, an optical subcarrier processing (OSP) based scheme is proposed and experimentally demonstrated. A Twin-SSB Nyquist in lower-order QAM is firstly generated using an electro-optic approach. OSP-based data aggregation is then deployed to coherently merge two sidebands in the twin-SSB to synthesize an SSB Nyquist QAM with an increased modulation level. The proposed scheme effectively relaxes the requirement for the digital-to-analog (DAC) resolution, thus reducing the power consumption and cost. Besides, the use of the coherent two-carrier pump in the data aggregation avoids the introduction of phase noise from the pump. It allows for the deployment of a low-cost laser as a pump laser source without sacrificing the performance, further reducing the overall implementation cost. Moreover, a hierarchical blind phase search algorithm is proposed to combat the possible distortions introduced in the data aggregation. A 12.5 Gbps SSB Nyquist 16QAM is experimentally synthesized from a 2 × 6.25 Gbps twin-SSB Nyquist QPSK with an error-free operation.

Communication module packaging

Abstract: A communication module may include a communication ground layer. The communication module may also include a circuit board. The circuit board may be located proximate the communication ground layer. The circuit board may include a stitch layer. The stitch layer may be electrically coupled to the communication ground layer via a plurality of stitch layer vias. Additionally, the communication module may include multiple ground vias. The ground vias may be electrically coupled to a portion of the circuit board and to the communication ground layer.