Development Of Arrayed Waveguide Grating And Tunable Optical Dispersion Compensator

Dense wavelength division multiplexer (DWDM) based on arrayed waveguide grating(AWG) is widely used in the backbone, metropolitan, and access networks, for itsadvantages of small channel spacing, easy integration with other optical components,compact size, high reliability, high yield, and low cost. In the recent years, most effortswere paid in the AWGs with low cost and athermal packaging technologies. Further more,more and more attentions were paid in the multiple channel tunable optical dispersioncompensator (TODC) based on AWG with the development of40Gbps systemts. For thesereasons, we did some researches and made the following innovations:In this thesis, we experimentally studied the thermal stresses in curve diced AWG chipintroduced by the differences between the linear expansion coefficient of AWG and those ofthe heater and the packaging box, and we introduced a new low thermal stress AWGpackaging. In this packaging, the AWG chip was bonded to the heater by heater conductivesilicon greese and silicon rubber, so the stress was very small which was caused by thethermal expansion coefficient difference between the AWG chip and the heater. Aborosilicate glass plate was bonded to the ceramic heater, and the ribbon fibbers werebonded to it with silicon rubber. For the linear expansion coefficient difference between theborosilicate glass plate and ribbon fiber is very samll, the thermal stress of ribbon fibber orAWG chip is very small. Further more, this new pakaging can assure that the AWG in thepackaging case will not be influenced by the forces outside of the case. Experimentalresults showed the typical center wavelength variation introduced by the thermal stress forthermally stabled AWG modules manufactured with this technique was smaller than5pm,when the ambient temperature varied from-20℃to65℃.We introduced a new athermalized AWG packaging. In this athermal AWG, two plaes Aand B with the same thermal expansion coefficient as AWG chip were adhered to thealuminium alloy compensation bars with large thermal expansion coefficient, and two parts(A and B)of AWG chip were adhered to the plate A and B, repectively. The part A and B ofAWG chip were fabricated by cutting a curve-shape AWG chip from the center of its inputslab waveguide. For the thermal expansion coefficient of compensation bar is larger than thatof AWG chip, the position between the AWG part A and B varies with the variation of theambient temperature, so the AWG center wavelength variation caused by the variation of the ambient temperature can be reduced. For this new athermal AWG have no any flexibility, itcan not be influenced by the outside force. And for the curve-shape AWG center wavelengthcan be adjusted by the radial stress, the center wavelength of this athermal AWG can beadjusted during packaging process, which can be used to compensate the center wavelengthvariation introduced by the mechanical and thermal stress. The experiment results showedthe coefficient of center wavelength varying with the ambient temperature was as small as-0.79pm/℃, when the ambient temperature varied from-5℃to70℃A novel compact AWG based on low refractive index contrast silica-on-silicontechnology is proposed. In this AWG, only the segments connected with slab waveguides inthe input and output waveguides are air trench (AT) waveguides. By using these ATsegments, the distance between the adjacent output waveguides connected with the outputslab is decreaced greatly, so the size of AWG chip is decreased dramatically. The segmentscoupling to fibers in the input or output waveguides and the arrayed waveguides are allfabricated with low refractive index contrast waveguides, for the purpose to obtain lowcoupling loss with fibers and good performances as traditional SOS AWGs. The designresuts show that the size of an AWG designed consisting of40channels on100GHz ITUgrid is very small, and forty-nine pieces of square AWG dies can be cut from a six inchsilicon wafer.This thesis proposes an integrated tunable optical dispersion compensator whichconsists of an AWG with air trench output waveguides and waveguide-type phasemodulators based on thermo-optic effect. The air trenches are formed on both sides of eachoutput waveguide to minimize the size of AWG. One TODC design for compensatingchromatic dispersion (CD) channel by channel with a tunable range from-402ps/nm to402ps/nm and another TODC design for compensating chromatic dispersions of multiplechannels simultaneously with a tunable range from-783ps/nm to783ps/nm are introduced.Finally, a TODC consisting of two cascaded TODCs is analyzed, which peak-to-peak groupdelay ripple is as low as0.9ps, when its CD can be tuned from-776ps/nm to776ps/nm.