A Tunable Lyot Birefringent Filter With Variable Channel Spacing and Wavelength Using Nonlinear Polarization Rotation in an SOA

Semiconductor optical amplifier pattern effect suppression using Lyot filter

“…The important characteristic it exhibits is the cosine-squared periodic comb-like profile, with the null points situated midway between adjacent transmission peaks whose wavelength spacing or free spectral range (FSR) is approximately 1.2 nm. This finding agrees well with the theoretical value calculated from [7] If the transmission peak of the filter is negatively detuned by a relatively small amount Dl, with respect to the optical carrier, then the spectral components of the amplified pulses that have been shifted to longer wavelengths owing to SPM [3,4], as shown in Fig. 3c, will be aligned with the sharp notches of the Lyot filter response.…”

“…The relative attenuation imposed by these notches is approximately 24 dB across the entire tuning range, thereby being attenuated in direct analogy to the degree of their shift. This can be done practically by choosing first the appropriate PMF length to adjust the FSR through a trial and error procedure that relies on the AM extent and the efficiency with which it must be reduced, and then rotating the wave plates to introduce the additional phase shift, Dw, in order to vary Dl up to 50% of the FSR according to Dl ¼ (Dw/2p) FSR [7]. In this manner, the Lyot filter can suppress the red-shifted spectral components, as shown in Fig.…”

“…If the unwanted frequency-shifted components are appropriately suppressed then the pattern-dependent distortion on the amplified data stream can be cancelled as reported in [4][5][6]. In this Letter we propose to implement this technique using a Lyot filter [7] to greatly reduce the pattern effect on a 10 Gbit/s return-to-zero (RZ) data pulse stream amplified by an SOA. Such Lyot filters have previously only been used for signal processing [8] and in multi-wavelength lasers [9].…”

A wavelength spacing switchable and TUNABLE high‐birefringence fiber loop mirror filter

“…To enhance the operational flexibility and functionality of the devices in configurable and dynamic environment, the tunability and switchability of the wavelength spacing are highly desirable. Different approaches have been demonstrated to realize the tuning and switching function, including modified Mach–Zehnder interferometers , circulator‐based bidirectional transit , nonlinear polarization rotation in an SOA , and HB fibers . Conversely, to accommodate the exploded bandwidth demand in DWDM network systems, the commonly used approach is to decrease the wavelength spacing by half and quarter (i.e., from 200 to 100 GHz, then down to 50 GHz) .…”

Temperature-sensitive dual-segment polarization maintaining fiber Sagnac loop mirror

“…This is normally done using a PC [6][7][8][9]. Besides the mechanical control by the PC, some literatures also reported on optically [10,11] and thermally [12] controlled FLM. However, most of those schemes are proposed based on a common goal-to enhance the spectral spacing tune-ability without altering the system configuration or replacing the PMF to a different PMF length.…”