350 research outputs found

    Single integrated device for optical CDMA code processing in dual-code environment

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    We report on the design, fabrication and performance of a matching integrated optical CDMA encoder-decoder pair based on holographic Bragg reflector technology. Simultaneous encoding/decoding operation of two multiple wavelength-hopping time-spreading codes was successfully demonstrated and shown to support two error-free OCDMA links at OC-24. A double-pass scheme was employed in the devices to enable the use of longer code length

    Design and Development of an Optical Chip Interferometer For High Precision On-Line Surface Measurement

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    Advances in manufacturing and with the demand of achieving faster throughput at a lower cost in any industrial setting have put forward the need for embedded metrology. Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the workpiece. Providing closer integration of metrology upon the manufacturing platform will improve material processing and reliability of manufacture for high added value products in ultra-high-precision engineering. Currently, almost all available metrology instrumentation is either too bulky, slow, destructive in terms of damaging the surfaces with a contacting stylus or is carried out off-line. One technology that holds promise for improving the current state-of-the-art in the online measurement of surfaces is hybrid photonic integration. This technique provides for the integration of individual optoelectronic components onto silicon daughter boards which are then incorporated on a silica motherboard containing waveguides to produce a complete photonic circuit. This thesis presents first of its kind a novel chip interferometer sensor based on hybrid integration technology for online surface and dimensional metrology applications. The complete metrology sensor system is structured into two parts; hybrid photonic chip and optical probe. The hybrid photonic chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. Optical probe is a separate entity attached to the integrated optic module which serves as optical stylus for surface scanning in two measurement modes a) A single-point for measuring distance and thus form/surface topography through movement of the device or workpiece, b) Profiling (lateral scanning where assessment of 2D surface parameters may be determined in a single shot. Wavelength scanning and phase shifting inteferometry implemented for the retrival of phase information eventually providing the surface height measurement. The signal analysis methodology for the two measurement modes is described as well as a theoretical and experimental appraisal of the metrology capabilities in terms of range and resolution. The incremetal development of various hybrid photonic modules such as wavelength encoder unit, signal detection unit etc. of the chip interferometer are presented. Initial measurement results from various componets of metrology sensor and the surface measurement results in two measurement modes validate the applicability of the described sensor system as a potential metrology tool for online surface measurement applications

    Design of weak 1-D bragg grating filters in SOI waveguides using volume holography techniques

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    To answer the growing need for more versatile integrated spectral filters, we show that weak one-dimensional gratings can be designed towards any desired target spectrum. We follow a very straightforward design procedure to demonstrate the performance of these devices. Measurements and simulations show a very good correspondence with the target spectra. By analyzing the results, we also found that the design procedure can be refined by using simulated reflections, instead of relying on the calculated Fresnel reflections

    Optical-CDMA in InP

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    This paper describes the InP platforms for photonic integration and the development on these platforms of an optical code division multiple access (O-CDMA) system for local area networks. We demonstrate three building blocks of this system: an optical pulse source, an encoder/decoder pair, and a threshold detector. The optical pulse source consists of an integrated colliding pulse-mode laser with nearly transform-limited 10 Gb/s pulses and optical injection locking to an external clock for synchronization. The encoder/decoder pair is based on arrayed waveguide gratings. Bit-error-rate measurements involving six users at 10 Gb/s showed error-free transmission, while O-CDMA codes were calibrated using frequency resolved optical gating. For threshold detection after the decoder, we compared two Mach--Zehnder interferometer (MZI)-based optical thresholding schemes and present results on a new type of electroabsorber-based MZI

    Monolithically integrated mode-locked ring lasers and Mach-Zehnder interferometers in AlGaInAs

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    In this thesis, monolithically integrated photonic devices for next generation optical telecommunications networks were investigated, namely semiconductor modelocked ring lasers and Mach-Zehnder interferometers operating at 1550 nm. Fabricated on the aluminium quaternary, the 2.3mm long passively mode-locked ring devices produced 1 ps pulses at a repetition rate of around 36GHz. It was found that the symmetrically placed dual saturable absorber configuration lead to the largest area of stable mode-locking, agreeing well with theoretical predictions in the literature. Optical harmonic injection mode-locking was found to improve the pulse timing stability, with a reduction in the radio frequency 3 dB linewidth from 1.4MHz down to 108 kHz, indicating a vast improvement in timing jitter. The sputtered SiO2 quantum-well intermixing technique allowed for the realisation of both symmetric and asymmetric arm length Mach-Zehnder interferometers, which were demonstrated as an electro-optic switch, tunable wavelength filter and optical code division multiple access encoder/decoder. The work concluded with the monolithic integration of a mode-locked ring laser and asymmetric Mach-Zehnder interferometer to demonstrate a simple, yet effective, photonic integrated circuit
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