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By filling the liquid crystal (LC) in the air holes of a photonic crystal fiber (PCF) with 8 mm length, a compact multi-band thermal optical switch is proposed here including two important telecommunication band, i.e., 1265 to 1317 nm and 1508 to 1568 nm. Within the bandwidth, the extinction ratio can be as high as 30 dB. Under the combined action of the bandgap-guiding mechanism and the interference effect, a temperature change of only 1 °C after clearing temperature ( Tc ) of the LC induces multi-band thermal optical switch of the LC-filled PCF. It is also noted that the transmission spectrum of the LC-filled PCF is quite sensitive to the ambient temperature. The consequent thermal sensitive is 3.9 nm/°C, making it a very good candidate for monitoring the temperature herein.

A novel method of extracting input pump powers from pump power integrals with high efficiency is proposed for the first time. In this method, a set of coupled nonlinear equations of input pump powers for given target pump power integrals are constructed. Finding the input pump powers corresponding to the target pump power integrals becomes finding solution of this set of nonlinear equations. A modified Newton's root-finding method is adopted to solve the nonlinear equations. To verify the proposed method, the input pump powers of a broadband (10 THz) Raman fiber amplifier that contains 100 signal channels and is counter pumped by 4 pumps is searched for given target pump power integrals. It is demonstrated that 3 iterations are enough for the method to achieve a satisfactory convergence. Compared with the previously reported techniques where hundreds of iterations are usually involved, the proposed method reduces the computational effort by two orders of magnitude.

A novel radiative optical isolator and a circulator are discussed in this paper. It is numerically estimated that with /spl lambda/=1.3 /spl mu/m, 45-dB isolation ran be achieved with an isolator of 8 mm in length. For a 21.5-mm-long 4-port circulator, the achievable isolation is about 45 dB, with approximately 1-dB insertion loss.