An ultrahigh-Q, tunable optical filter with a FWHM bandwidth of 41 MHz is demonstrated. The filtering is produced by nondegenerate phase conjugation through four-wave mixing in atomic-sodium vapor. The filter is observed to have a maximum quantum efficiency of 4 x 10(-3). However, degenerate phase-conjugation experiments in sodium suggest that a quantum efficiency of greater than unity can be a...

In this paper we have proposed a highly tunable spectrum sliced photonic microwave band pass transversal filter for microwave and millimeterwave frequency applications. This filter configuration is based on two cascaded Fabry-Perot filters with different free spectral range and a broadband optical source. The high tunability of the filter is achieved by carefully choosing free spectral range of...

Abstract Measurements on a passive optical fibre tunable filter are presented. The device is based on a loop mirror in a ring resonator. The loop mirror allows tuning by changing the coupling coefficient of a coupler. The novel fiter structure allows planar optical integration for having higher free spectral ranges. Novel and simple design equations for the fiter parameters and the tuning proce...

An Er"+-doped fiber ring laser with unidirectional operation without optical isolator has been investigated for different cavity conditions. The fiber ring laser cavity is built in such a way that the optical fields propagating in the two directions suffer different losses. As a consequence, the laser oscillation appears in a quasi-unidirectional form. By incorporating a fiber pigtailed bandpas...

A widely tunable erbium-doped all-fiber laser has been demonstrated. The tunable mechanism is based on a novel tunable filter using multimode interference effects (MMI). The tunable MMI filter was applied to fabricate a tunable erbium-doped fiber laser via a standard ring cavity. A tuning range of 60 nm was obtained, ranging from 1549 nm to 1609 nm, with a signal to noise ratio of 40 dB. The tu...

We have developed a wideband tunable optical filter that uses a long-period fiber grating (LPFG) in which both resonance wavelength and its signal attenuation can be adjusted. We create the grating mechanically by pressing a spring coil to an optical fiber. We achieve continuous fine tuning of wavelength and attenuation by varying the temperature of the LPFG. The adjustable ranges of the LPFG a...