Performance Analysis of a Multi-Function Mach-Zehnder Interferometer Based Photonic Architecture on SOI Acting as a Frequency Shifter

A photonic frequency shifter based on generalized Mach-Zehnder interferometer (GMZI) architecture is presented and experimentally validated. The circuit consists of four Mach-Zehnder modulators (MZM) in a 4 × 4 network bounded by two 4 × 4 multimode interference couplers and functionally equivalent to two parallel dual-parallel MZM (DP-MZM). The circuit can offer static bias free operation, virtual connectivity control of the components, and spatial separation of up- and down-converted carriers, which can be collected from separate ports without using any optical demultiplexing filters. Thus, the design permits remote heterodyning (advantages which cannot be obtained using a commercial DP-MZM or filter based optical frequency shifter). Experimental investigation shows deviation from ideal performance due to possible fabrication error and poor fiber-chip coupling. A carrier suppression of >20 dB and spurious sideband suppression >12 dB relative to the principal harmonics is achieved without any tuning for bias adjustment. In addition to the frequency conversion, the integration feasible circuit can also perform as a sub-carrier generator, IQ modulator, and frequency multiplier.

Optical Fiber Sensor for Temperature and Strain Measurement Based on Multimode Interference and Square-Core Fiber

A variety of specialty fibers such as no-core fiber (NCF) have already been studied to reveal their sensing abilities. In this work, we investigate a specialty fiber, square-core fiber, for temperature and strain sensing. A simple single-mode–multimode–single-mode (SMS) fiber sensor was fabricated, consisting of a 30-cm-long square-core fiber. The experimental results indicate that the maximal wavelength-temperature and wavelength-strain sensitivities are −15.3 pm/∘C and −1.5 pm/με, respectively, while the maximal power-temperature and power-strain sensitivities are 0.0896 dBm/∘C and 0.0756 dBm/με. Analysis of the results suggests that the fiber sensor has the potential to be used as a high-sensitivity temperature sensor with a low strain sensitivity.