ROCKY MOUNTAIN SECTION OPTICAL SOCIETY OF AMERICA
                              &
           IEEE LASERS AND ELECTROOPTICS SOCIETY


                      Oct. Meeting

Date:  Thursday, 15 Oct. 1998
Time:  7:00 PM refreshments, 7:30 PM talk
Place: National Institute of Standards and Technology
       325 Broadway, Boulder, CO
       Room 1107


Measurements of arrayed-waveguide gratings (AWGs) at NTT OptoElectronics Labs-
Ibaraki, Japan

       Steven Mechels
       NIST Optoelectronics Division



Abstract:

I will introduce the operational principle of AWGs and give the context for 
their use in wave-division multiplexed (WDM) systems.  Interchannel crosstalk is 
one of the largest technical challenges remaining in AWG production. Phase error 
which is present  in the AWG delay arms is the major contributor. Low coherence 
optical techniques can be used to measure this phase error and compensation can 
be performed to reduce crosstalk to -35 dB. I'll introduce this technique and 
discuss my work which involved theoretically compensating for dispersion in 
order to perform these measurments. I also built an optical low coherence 
reflectometer to measure the internal reflectances of AWGs. Interesting 
reflections occur from polyimide halfwave plates (used to eliminate AWG 
birefringence effects) and are also a function of the specific AWG design. Fiber 
arrays are attached as angled-block units and have reflectances of -70 dB. 
Finally, I'll present some preliminary work done using AWGs as encoding/decoding 
devices in coherent code-division multiple access (CDMA) systems. This 
illustrates how AWGs can be used for spectral waveform tailoring and frequency 
filtering.



Biography: