A compact three‐wavelength narrow‐linewidth fiber laser with single pump is demonstrated. The multiple‐wavelength output signal can be effectively employed to synthesize large effective probing wavelength of up to 1.16mm for high depth resolution digital holography.

Dynamic wavelength switching of a phase-shifted fiber grating cavity with electrical pulses is studied experimentally and numerically. Simulations accurately describe observations. The effect of acoustic oscillations and fiber Bragg grating cavity refilling explains the results.

Fibers with internal electrodes are driven electrically. They allow for the control of polarization, wavelength tuning, nanosecond light gating, Q-switching and mode-locking of lasers. These are some of the applications discussed in this paper.

An electrically controlled high-speed all-fiber switch is investigated. It is based on a monolithic Mach-Zehnder interferometer using a Gemini fiber. The fiber is provided with internal electrodes for active control of the phase using high-voltage electrical pulses. The demonstrated switching speed is 20 ns. The monolithic design guarantees that the off- and on-states are attained simultaneously for a broad range of wavelengths (50 nm). The interferometer can be switched-off using a second electrode, providing a 15 ns long optical pulse.

A twin-core fiber Michelson interferometer is evaluated as a high-temperature sensor. Although linear and reproducible operation up to 300°C is obtained, at higher temperatures (700°C) the refractive index shifts plastically and hysteresis is observed, rendering an untreated sensor head unusable. The shift is shown to be greatly reduced by an annealing process of the fiber for 10 h at 900°C, with which the linear response is preserved.

Fiber modulators with strong field recorded exhibit the linear electrooptic effect. Interferometry transforms phase- into intensity modulation. Vπ 100-V is obtained, with an electrical bandwidth of tens of MHz. Applications and limitations are discussed.

In this paper, we give an overview of recent results on switching of light in fibers with internal electrodes. Polarization rotation, nanosecond gating, and wavelength switching in fiber Bragg gratings and in long period gratings are discussed. Applications are exemplified in Q-switching fiber lasers and in RF-signal filtering.

We fabricate a Gemini fiber with two branches bound by a glass bridge to create a stable monolithic Mach-Zehnder fiber interferometer and demonstrate the function of add-drop multiplexing with flat response over the entire C-band.