K.S. Chiang

Birefringence in benzocyclobutene strip optical waveguides

We report the fabrication of benzocyclobutene strip optical waveguides and the measurement of their birefringence properties. To take into account the stress-induced birefringence in the waveguide, we generalize the formulas reported previously for the analysis of strip waveguides. Our experimental results are shown to agree closely with the theoretical calculation. The condition for achieving zero modal birefringence by control of the aspect ratio of the strip of the waveguide is highlighted. The dependence of the birefringence in the waveguides on the temperature is also measured and discussed.

Ultra-large-core single-mode fiber for optical communications: the segmented cladding fiber

In conclusion, we have analyzed a 50 /spl mu/m-core segmented cladding fiber, which is capable of providing single-mode operation from 0.90 /spl mu/m to 1.70 /spl mu/m. We have elucidated the physical principle of the fiber with the radial effective index method whose accuracy has been confirmed with the finite-element method. The effective core area of the fiber is larger than those of any other large-core fiber designs by at least one or two orders of magnitude. We believe that we have opened up a new approach of designing ultra-large-core single-mode fibers for optical communications. The chromatic dispersion of the fiber and its control, as well as the bending loss and other practical issues are being studied.

Magneto-optical electric-current sensor with enhanced sensitivity

In this design note, an air-gapped ring core type Faraday-effect optical current sensor using a new sensing element design is described. The sensing element is a finely polished glass prism with highly reflective coatings on the two end surfaces, which is designed in such a way that the light beam propagating through it undergoes 20 critical-angle reflections at the glass-air interfaces. The current sensitivity of this new design is almost three times higher than that of a previous design based on a similar principle.

Lithium–Niobate Channel Waveguide for the Realization of Long-Period Gratings

We propose a special lithium-niobate (LiNbO3) single-mode waveguide for the realization of long-period gratings, which consists of a channel core embedded in a thin slab cladding. We fabricated the waveguide on a z-cut LiNbO3 substrate with a two-step proton-exchange process and demonstrated its suitability for grating application with a number of removable photoresist long-period gratings deposited on the waveguide surface. The waveguide fabrication process and the LiNbO3 waveguide structure could be further explored for the development of electrooptic gratings for high-speed applications.

Theory of nondegenerate four-wave mixing in a birefringent optical fibre

Nondegenerate four-wave mixing in a birefringent optical fibre pumped with two waves of orthogonal linear polarisations at different wavelengths is studied theoretically. It is shown that, under appropriate conditions, the frequency shift in the four-wave mixing process is proportional to the polarisation-mode dispersion in the fibre, and insensitive to the difference between the two pump wavelengths. The theory explains the recent experimental observation that a laser beam can mix with a spectrum of light in a birefringent fibre to generate a distinct frequency-shifted beam.

Multiwavelength erbium-doped fiber laser with a high-birefringence fiber loop mirror

Summary form only given. With the rapid development of wavelength-division-multiplexed systems in optical communication, multiwavelength laser sources have attracted considerable interest. Several types of multiwavelength rare-earth-doped fiber lasers have been demonstrated, which differ in the wavelength-selection methods used. The wavelength selective elements that have been used in these lasers include a Fabry-Perot etalon, fiber Bragg gratings, a wavelength-division multiplexer, a multimode fiber placed in a single-mode fiber ring cavity, a high birefringence (HiBi) fiber standing cavity, and a HiBi fiber ring cavity. We present a novel multiwavelength erbium-doped fiber laser, in which wavelength selection is achieved with a HiBi fiber loop mirror.

An electric-current sensor employing twisted fibre with compensation for temperature and polarization fluctuations

A sensor for alternating electric current measurement based on optical Faraday rotation with a specially designed twisted fibre is reported. A signal processing technique is demonstrated to stabilize the sensor output against temperature variations and polarization fluctuations in the fibre. The current sensitivity measured experimentally is , in good agreement with the theoretical value.

Remote high temperature sensing with a reflective bandpass long-period fiber grating and a fiber ring laser

We demonstrate a remote high temperature fiber sensing system, where the sensing element is a long-period fiber grating (LPFG) fusion-spliced to a short section of a hollow-core fiber (HCF) and sensor interrogation is achieved with a fiber ring laser. The HCF turns the LPFG from a band-rejection filter into a reflective bandpass filter, while the ring laser selects the reflected wavelength from the LPFG sensor. Our experimental sensor shows a sensitivity of 0.095 nm °C−1 over the temperature range from 150 to 600 °C and the sensing distance is about 1 km.

Imprinting of thermo-optic polymer-waveguide Mach-Zehnder interferometer with bottom-up electric heating

We demonstrate a new approach of fabricating a thermo-optic polymer-waveguide Mach-Zehnder interferometer (MZI). The MZI is fabricated with an imprinting technique, where the electrode heater is formed at the bottom of the waveguide substrate.

Dynamic gain flattening of an erbium-doped fiber amplifier using a high-birefringence fiber loop mirror

A flexible method based on a high-birefringence fiber loop mirror is proposed for the gain flattening of an erbium-doped fiber amplifier. The gain profile was flattened to within /spl plusmn/0.9 dB over a 33 nm bandwidth.