Optical Heterodyne Measurement of Terahertz Wave

One of the most notable frequency regions in terms of research currently lies in the ‘frequency gap’ region between microwaves and infrared: terahertz wave. Although new methods for generating and detecting terahertz wave have been developed, few detectors operating at room temperature are able to capture low-energy terahertz beams. Here we introduce the optical heterodyne measurement (nonlinear frequency up-conversion detection) of terahertz wave using parametric wavelength conversion in a nonlinear crystal; this has better sensitivity than many commonly used thermal detectors such as pyroelectric detectors. Additionally, optical heterodyne techniques allow the beams of terahertz wave to be visualized and their frequency and intensity determined directly as visible light. These are very promising for extending applied researches into the terahertz region, and we expect that these will open new research fields such as wireless information communications or non-destructive inspection in the terahertz region.

High Capacity 64-Quadrature Amplitude Modulation Based Optical Coherent Transceiver for 60 GHz Radio Over Fiber System

Today’s world demands for maximum bandwidth utilization in the area of optical fiber network to achieve serious progress due to data consumption has been grown by > 25% as compared to last year. 5G system is one of the promising technology cater for high bandwidth utilization between multiple transceivers and have the advantages to operate in the milli-meter wave (mm-wave) of 60 GHz. There is much interest of photonic technique such as optical heterodyne coherent detection to produce mm-wave frequencies. We propose a 60 GHz radio over fiber (RoF) link using 168 Gb/s high capacity input data rate based 64-Quadrature amplitude modulation (64-QAM), coherent detection using optical heterodyning and advanced digital signal processing (ADSP) based system. An optimized version of optical heterodyne technique is used to derive 60 GHz radio frequency (RF) signal for connecting radio nodes over wireless link. In order to compensate the irregularities effect of standard signal mode fiber (SSMF), a novel ADSP technique is used which allows good improvement in the spectral signal efficiency and achieved longer distance communication. The ADSP technique plays a key role to achieve high capacity data rate requirements for forthcoming 5G technologies. The proposed RoF system shows that an error free transmission is accomplished over 170 km SSMF and achieved BER is 2.7×10-3 against 7.015 % error vector magnitude (EVM) with 30 dB Signal to Noise ratio (SNR).

All-Fiber Frequency Shifter Based on an Acousto-Optic Tunable Filter Cascaded with a Tapered Fiber-Coupled Microcavity

An all-fiber acousto-optic frequency shifter (AOFS) based on an acousto-optic tunable filter (AOTF) cascaded with a packaged tapered fiber (TF)-coupled microsphere was proposed and demonstrated in both theory and experiment. The configuration has the advantages of easy alignment, robustness, compact size, and low cost, which will improve its further application, such as in the optical heterodyne detection technique (OHDT).