Passive Optical Networks

of the central wavelength can be made zero. In [26], the temperature dependence of

the TM and TE mode of the central wavelength of a polarization dependent AWG

with an attached bimetal plate was measured and is shown in Fig. 3.24. With the

bimetal plate, the TM and TE modes had an average temperature dependence of

less than 0.001 nm/8C and 0.004 nm/8C, compared to 0.013 nm/8C for the con-

ventional AWG. A side effect due to the attachment of the bimetal plate to the

silicon substrate of the AWG is the shift in central wavelength due to the initial

stress, which needs to be accounted for in an AWG layout.

Athermal AWGs of up to 40 channels [27–30]