A Simple All-Fiber Solc Filter Based on 45°-Tilted Fiber Gratings

A simple all-fiber Solc filter (AFSF), which consists of two 45°-tilted fiber gratings (45°-TFGs) UV-inscribed in the polarization-maintaining fiber (PMF) and a series of PMF cavities, is proposed and demonstrated. The performance of the proposed filter has been theoretically simulated and experimentally verified. Both the simulated and experimental results show that the bandwidth of the filter could be tuned by the PMF sub-cavity length and the number of PMF cavities. And the free spectral range (FSR) only depends on the sub-cavity length. As a proof of that, the bandwidths of AFSF with different number of PMF sub-cavity (N=2, N=3, N=4) and the same PMF sub-cavity length of 30cm are 4 nm, 2.6nm, and 2nm, respectively. The FSRs of 3-stage AFSF with different PMF sub-cavity length (L=20 cm and L=40 cm) are 15.3 nm and 7.97 nm, respectively. Furthermore, we have also investigated the tunability of the AFSF by controlling the temperature of PMF cavity with a tuning sensitivity around 1.205 nm/°C. Compared with existing fiber-optic Solc filters, the AFSF with prominent advantages such as extremely simple and robust structure, thermal tunability in wavelength, and low cost will bring a bright future for applications in optical communication and sensing systems.