Patrik Rugeland

Photonic scanning receiver using an electrically tuned fiber Bragg grating

A 5-cm-long electrically tuned fiber Bragg grating is used to filter a microwave signal on an optical carrier at 1.55 mum. A chirped distributed-feedback structure is employed, with a transmission bandwidth of 54 MHz and relative optical carrier rejection of >30 dB for rf frequencies >2 GHz. The rapid monotonic sweep of the Bragg wavelength is translated into a fast-frequency sweep for rf analysis.

Revisiting twin-core fiber sensors for high-temperature measurements.

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.

Visible light guidance in silica capillaries by antiresonant reflection

Hollow silica capillaries are examined as optical waveguides evaluating the antiresonant reflecting optical waveguide (ARROW) effect by sequentially reducing the wall thickness through etching and measuring the optical transmission. It is found that the periodicity of the transmission bands is proportional to the wall thickness and that the propagation loss is of the order of a few dB/m.

High-speed electrical switching in optical fibers [Invited]

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.

Temperature characteristics of the birefringence properties of filled side-hole fibers

The temperature characteristics of the birefringence of side-hole fibers filled with liquids or metal are investigated, aiming at providing a basis for on/off temperature sensing. Short pieces of fiber are filled and the change in birefringence is registered using measurements in reflective mode of the transmitted power through a linear polarizer at 1550 nm. The rapid change in the birefringence behavior of the fiber at the temperature of the phase transition of the filler substance is shown, and from the measurement data the phase transition temperatures can be determined as well as an estimation of the birefringence change with temperature. The experimental results are supported by numerical simulations.

Monolithic Interferometers Using Gemini Fiber

Gemini fibers are used to fabricate monolithic interferometers. The thermal stability of a monolithic Michelson interferometer is found to be superior to that of a conventional fiber ribbon interferometer. The fabrication of fused couplers, fiber Bragg gratings, and a broadband Mach-Zehnder add-drop multiplexer are demonstrated using the novel fiber.

Nanosecond monolithic Mach-Zehnder fiber switch

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.

Tunable Photonic Microwave Generation Based on a Novel Dual-Polarization Fiber Laser Cavity

A novel dual-polarization fiber laser is proposed by incorporating a distributed feedback grating inscribed in a twin-hole fiber with internal electrodes. Dual-polarization lasing is achieved with a spectral separation of ~42 pm. By beating the optical waves at a photodiode, a microwave signal at ~5.244 GHz is achieved with a signal-to-noise ratio ~45 dB. An electrically tuned microwave signal with a tunable range of 150 MHz is demonstrated.

Component and setup for insertion of gases in a hollow-core optical fiber sensor

An optical fiber component and setup were developed to insert and remove gases from hollow-core optical fibers, allowing gas/light mixing over the length of the fiber for gas sensing applications. Transmitted signals acquired at the output of the fiber contain information regarding absorption occurring inside the fiber, providing a spectroscopic signature of the gas or gases in the fiber. Spectra for 1 atm of acetylene (C2H2) around 1525 nm and 1 atm of carbon dioxide (CO2) around 1432 nm were obtained and compared to HITRAN data, showing good agreement. The setup can also be used to prepare gas cells.

Electrically controlled fibers

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.