What type of AWG do you have, and by how much do you wish to change the centre frequency?

For small frequency shifts, temperature tuning may be an option.  Some AWGs use a Peltier device to stabilise the temperature, offering a means to control the centre wavelength.

Many manufacturers put a great deal of effort into making their AWG devices athermal, in which case temperature tuning is unlikely to be effective. 

If the frequency shift is from one ITU channel frequency to another, then an optical switch to select an appropriate port on the remote AWG is an option.

Alternatively, the AWG can be specifically designed with a large temperature coefficient to allow tuning over a wide frequency range, for example as described by Zhang et. al.

Another approach is to employ a liquid crystal as the tuning mechanism, as reported by NTT, Dai and others.

Horn et. al. fabricated in Lithium Niobate for an electrically tunable device.

http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=1077991

http://ieeexplore.ieee.org/document/4528757/

https://www.osapublishing.org/aop/abstract.cfm?uri=OEDI-2014-OTh4C.8

https://www.osapublishing.org/oe/viewmedia.cfm?uri=oe-20-24-26922

See my paper: Dieckröger, J., März, R., Clemens, P.C., Heise, G., Schneider, H.W.

Thermooptically Tunable Optical Phased Array in SiO2-Si

(1999) IEEE Photonics Technology Letters, 11 (2), pp. 248-250. 

What type of frequency shift are you looking for (range). Early AWGs could shifted in centre frequency by changing temperature - they were mounted on TECs. However, most of the current versions are athermal. What type of AWG do you have?

Also, are you working on a WDM PON - if so what is the spacing between the WDM channels. If it is large enough you might be able to use other filtering options at the RN.