|
A new arrayed wave-guide demultiplexer is proposed on Proton exchanged X-cut-Y propagating Lithium-niobate substrate. The device simulation is performed at 1550nm central wave length. The simulation is carried out using Optiwave 5.O based on the beam propagation method.and uses effective index method for calculating the propagation constant b.This novel device differs from the conventional AWG MUX/DEMUX. The width of the wave-guides in the array section is varied from 2.5µm to 4.0µm with a step size of 0.1µm keeping the length of all array wave-guides equal. This contributes to the dispersion effect.
The small 's' bend. sections are used at the i/p and the o/p array aperture. The dispersive effect at the i/p and o/p bend section is negligible. Hence the dispersion of the Phasar is mainly due to the increase in the width of the wave-guides in the array section. One of the merits of the device is the use of the variable Width wave-guides for controlling the effective index of the wave-guides in the array, which makes the device compact and reduces the optical propagation losses. In the conventional arrayed wave guide DWDM MUX/DEMUX the increase in the channel count Increases the cross talk that can be minimized by increasing the number of wave-guides in the array section, resulting in a complex structure. In the proposed device the spacing between the wave guides in the array section can be easily controlled by the “s” bend sections which in turn minimizes the cross talk [intra channel] without increasing the number of wave-guides in the array structure which limits the phase error.
As the device is Lithium niobate based, which exhibits an excellent electro optic behavior, the device can be made tunable contributing to the rapid development of high speed Broadband optical networks such as fiber to the home and Broadband optical networks such as fiber to the home and DWDM, apart from using it as a dynamic switching device.The simulated results at l=1550nm for X- cut Y propagating proton exchanged wave guide {PHASAR} for TE polarized light depicts the free spectral range in the order of THz. The simulation was performed for 4-channel demultiplexer having a channel spacing of 200GHz.
Due to the strong confinement in the array wave-guide structure, the field profile at the focusing point in the image plane maintains its shape. The modal field is assumed to be Gaussian and all the measurements are performed at (FWHM). The device has low diffraction order although it is used for broadband optical communication network This results in a low diffraction loss at the central channel. An attempt is made in the design to keep the focal field at the o/p a replica of the modal field at the i/p by choosing the symmetric I/P & O/P MMI coupler and the wave-guides. The non-uniformity is kept minimum by the optimization of position of the waveguides in the i/p and the o/p array aperture apart from using linear tapers at the i/p and o/p.
|
