We report on a wavelength-tunable filter based on multimode interference (MMI) effects. A typical MMI filter consists of a multimode fiber (MMF) spliced between two single-mode fibers (SMF). The peak wavelength response of the filter exhibits a linear dependence when the length of the MMF is modified. Therefore a capillary tube filled with refractive-index-matching liquid is used to effectively increase the length of the MMF, and thus wavelength tuning is achieved. Using this filter a ring-based tunable erbium-doped fiber laser is demonstrated with a tunability of 30 nm, covering the full C-band.

Tunable multimode-interference bandpass fiber filter

A rotating cutting head catheter for passage through chronic total occlusions or other refractory atherosclerotic plaque from diseased arteries is disclosed. The catheter's rotating cutting head is designed to reside safely within an outer protective sheath when not in use. The outer protective sheath contains one or more helical grooves or slots, and the cutting head contains protruding blades or projections that fit into these helical grooves or slots. Application of torque to an inner catheter or wire attached to the cutting head applies spin to the cutting head, and the force of the sheath's helical grooves or slots against the cutting head's protruding blades or projections advances the cutting head outward from the protective sheath. Once extended, the cutting head may now rotate freely. The device may use a guidewire to direct the cutting head to the desired position.

Catheter system and method for boring through blocked vascular passages

Catheter-based Optical Coherence Tomography (OCT) systems utilizing an optical fiber that is positioned off-axis of the central longitudinal axis of the catheter have many advantage over catheter-based OCT systems, particularly those having centrally-positioned optical fibers or fibers that rotate independently of the elongate body of the catheter An OCT system having an off-axis optical fiber for visualizing the inside of a body lumen may be rotated with the body of the elongate catheter, relative to a handle portion The handle may include a fiber management pathway for the optical fiber that permits the off-axis optical fiber to rotate with the catheter body relative to the handle The system may also include optical processing elements adapted to prepare and process the OCT image collected by the off-axis catheter systems described herein

Catheter-based off-axis optical coherence tomography imaging system

Methods and apparatus for the active control of a wavelength-swept light source used to interrogate optical elements having characteristic wavelengths distributed across a wavelength range are provided.

Wavelength sweep control

We propose a tunable erbium doped fiber laser based on a Fabry-Perot (F-P) cavity tuned by an electrostatic actuator. The device is made of single crystalline silicon. The F-P cavity consists of two Bragg mirrors, one being displaced by a comb-drives actuator. The F-P cavity, grooves for optical fibers and electro-mechanical structure are fabricated by deep reactive ion etching on a 70 μm silicon on insulator wafer and are integrated in a ring fiber laser. The resulting tunable fiber laser has a tuning range of 35 nm in the C-band and a spectral width of less than 0.06 nm. The maximum applied voltage for full tuning of the laser is 37 V. The mechanical resonance frequency of the actuated mirror is 14.4 kHz allowing fast tuning of the laser. The maximum output power is 1.8 mW.

Tunable Fiber Laser Using a MEMS-Based in Plane Fabry-Pérot Filter

We report the development of a ring tunable fiber laser based on tunable fiber Bragg gratings (TFBG) integrated with an optical circulator. The TFBG is embedded inside a 3-piont bending device for wavelength tuning. The tunable laser operating in the C-band has power variation, tuning resolution, tuning range and laser line width of ±0.5 dB, 0.5 nm, 25.0 nm and less than 0.05 nm, respectively. As 40 mW of pump power is used, the ring tunable laser has a side mode suppression ratio of 60 dB and a power conversion efficiency of 25%. These specifications ensure the high-quality operation of a tunable laser.

C-band continuously tunable lasers using tunable fiber Bragg gratings

The invention provides a fiber-optic sensing system, utilizing a fiber-grating-based sensor, for a physical parameter, eg, a pressure or a temperature Different kinds of fiber-grating-based sensors may be used for this purpose but in-fiber gratings such as Fiber Bragg Grating, Long Period Grating and Surface Corrugated Long Period Fiber Grating are particularly suitable Due to the small size of the optical fiber and the fact that same fiber acts as the sensing element as well as the signal conducting medium, it is possible to install the sensor in a small diameter needle which is commonly used for medical diagnosis and treatment As a result, when the fiber-optic sensing system of the invention is used for in-vivo measurement of a biological parameter, such a sensing needle can be used for different in-vivo pressure or temperature sensing applications without causing too much harm and discomfort to the subject tested

Fiber-optic sensing system

This invention relates to a new technique of interrogating fiber grating sensors employed for measuring physical quantities such as temperature and force. The technique involves the edge filtering of transmitted light that occurs when a narrow bandwidth light of suitable wavelength from a laser source is passed through a Long Period Fiber Grating (LPFG). When the characteristics attenuation spectrum of the LPFG is shifting, an energy modulation effect will be achieved when one measures the intensity of the transmitted narrow bandwidth light. The narrow bandwidth strong light is best obtained by the reflection of a broad band light from a fiber Bragg gratings (FBGs). If the reflected narrow band spectrum from the FBGs is kept constant while the LPFG is subjected to temperature changes, applied loading or other type of suitable physical quantity changes, the characteristic transmission spectrum of the LPFG will shift according to the applied physical quantity, thus modulating the eventual transmitted light intensity. By transforming this intensity into a voltage signal, the variation of the physical quantity concerned can be deduced. Conversely, if the attenuation spectrum of the LPFG is kept constant and the FBG is subjected to temperature changes, applied loading or other type of suitable physical quantity changes, the same modulation effect will be achieved and the physical quantity concerned can likewise be monitored.

Chia-Chin Chiang

Papers

C-band continuously tunable lasers using tunable fiber Bragg gratings

Fiber-optic sensing system

Energy-modulating fiber grating sensor

Enhanced sensitivity of bare FBG pressure sensor based on oval-shaped 3D printed structure

Comparison of single and double cladding long period fiber grating sensor using an intensity modulation interrogation system