Font Size: a A A

Planar Waveguide Devices Based On Novel Arrayed Waveguide Gratings For Wavelength Division Multiplexing And Access Networks

Posted on:2010-03-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:T T LangFull Text:PDF
GTID:1118360302983080Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Upgrading telecommunication networks to increase their capacity is becoming increasingly important due to the rapid increase in network traffic. Wavelength division multiplexing (WDM) provides a new dimension for solving capacity and flexibility problems. Arrayed waveguide grating (AWG) is one of the most important components in WDM systems. It has many advantages, including small size, high reliability, easy integration and low cost. AWGs can be used to realize multiple functions, such as wavelength multi/demultiplexers, wavelength routers, channel monitors, optical add/drop multiplexer (OADM), and optical cross connect (OXC). Ever since its invention in 1980s, AWG is being studied around the world. The focus of this thesis is the design, simulation, fabrication and testing of wavelength division multiplexers and triplexers based on novel arrayed waveguide gratings.Fiber to the home (FTTH) has been developing rapidly in recent years and will become a major technology for next generation broadband access networks. An AWG based multiplexer has many advantages including small size, high reliability and low cost. The commonly used wavelengths for triplexers in fiber access networks are 1310nm, 1490nm and 1550nm. Because of the wide spectral range and very unequal wavelength spacings, it is difficult to produce satisfactory results with a conventional AWG design. In this thesis, a novel cross-order AWG design particularly suitable for triplexers is presented. The spectral periodicity of the grating is utilized so that the first wavelength works at a different diffraction order, and is transposed to a wavelength that is approximately in the middle of the second and third channels. This results in a reduced free spectral range (FSR) requirement and more equal distances between the output waveguides. Consequently, the AWG can operate at a higher diffraction order with a smaller overall size, compared to the one designed by conventional methods. Simulation and experimental results are presented. The measured spectra are consistent with simulation results, and confirmed the operation principle of the device.Polarization dispersion is an important issue in planar waveguide based wavelength (de)multiplexers for DWDM applications. For a conventional AWG based device, owing to the difference in the propagation constants of the TE (transverse electric) and TM (transverse magnetic) modes in planar waveguides, a polarization dependent wavelength shift (PDλ) occurs in the spectral responses. Several approaches have been developed to compensate the polarization dispersion, including the insertion of a half wave plate in the middle of the arrayed waveguides, non-birefringence waveguide design using a square cross-section, different waveguides in a triangular shaped patch area of the AWG, and the integration of a polarization compensator in the slab region. All those techniques suffer from problems ranging from fabrication difficulties to poor performance, or they are limited to specific structures and material systems. For silica based AWGs, a common method is to use doped silica in the upper cladding. However, this would degrade the long term stability and reliability of the device, and requires accurate control of the doping levels. In this thesis, a new design method for eliminating the polarization dispersion of AWGs is presented. By utilizing the birefringence difference between the slab waveguides and the arrayed waveguides, a polarization insensitive AWG can be realized without requiring any additional fabrication step. Simulation and experimental results confirmed the feasibility of this technique.Finally, the fabrication process for integrated optical devices, such as waveguide deposition, lithography, metal sputtering, lift off and dry etching, are studied. The devices are fabricated in silica-on-silicon material systems with a 6μm x 6μm buried channel waveguide structure. A set of reasonable fabrication conditions are gained. The fabrication and characterization of AWG demultiplexers are completed and good results are obtained.
Keywords/Search Tags:Wavelength Division Multiplexing (WDM), Arrayed Waveguide Grating (AWG), Polarization Dependent Wavelength Shift (PDλ), Fiber to the Home (FTTH), Triplexer
PDF Full Text Request
Related items