Showing papers by "Graham Town published in 2009"

Design considerations for short-wavelength operation of 790-nm-pumped Tm-doped fibers.

Abstract: Tm-doped 790-nm-pumped silica fiber lasers are excellent candidates for producing emission at <1.95 μm, but achieving efficient operation at these wavelengths requires careful attention to fiber design because of the characteristic three-level reabsorption effects. We present a discussion of methods for mitigation of these effects and two high-efficiency systems that are capable of producing up to 70 W at <1.92 μm.

Simplified millimeter-wave radio-over-fiber system using optical heterodyning of low-cost independent light sources and RF homodyning at the receiver

Abstract: A simplified, cost-effective millimeter-wave radio-over-fiber system is proposed by heterodyning two independent low-cost light-sources and RF homodyning at the receiver that suppresses phase-noise effects. Proposed system avoids phase/frequency locking, high-speed modulators and local oscillators/mixers in CO and BSs.

Ultrasensitive refractive index sensor based on twin-core photonic bandgap fibers

Abstract: We have theoretically investigated twin-core all-solid phot onic bandgap fibers (PBGFs) for evanescent wave sensing of refractive index within one single microflu idic analyte channel centered between the two cores. The sensor can achieve ultrahigh sensitivity by detecting the change in transmission. We find novel features in the sensing characteristics: the sensitivity is higher at the short wavelength edge of a bandga p than at the long wavelength edge, the effective index of the odd supermode (n odd ) is more sensitive to ambient refractive index change compared with that of the even supermode (n even ). Keywords: fiber sensor, photonic bandgap fiber, directional coupler 1. INTRODUCTION There is a growing research interest in optical fiber refractive index sensors and biosensors using the principle of evanescent wave sensing. Most effort has concentrated on increasing the sensitivity of fiber sensors to detect small refractive index changes. In this context, photonic crystal fibe rs (PCFs) have received consid erable attention recently, as PCF allows infiltration of the analyte into the air holes, thereby maximizing the interaction between the probing electromagnetic field and ambient analyte [1, 2, 3]. Furthermore, due to the flexibility of design and ease of fabrication, multi-core PCF is advantageous for applications in optical communication and sensing [4, 5, 6]. However, fiber sensors based on either conventional single mode fiber (SMF) or PCFs currently cannot compete with some other photonic sensors, e.g., surface plasmon resonance (S PR) sensors. The performance of fiber se nsors is currently limited either by the detection limit of around 10

Ultrasensitive twin-core photonic bandgap fiber refractive index sensor

Abstract: We propose a microfluidic refractive index sensor based on new polymer twin-core photonic bandgap fiber (PBGF). The sensor can achieve ultrahigh detection limit, i.e. ≫1.4×10−7RIU refractive index unit (RIU), by measuring the coupling wavelength shift.