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


                        Sept. Meeting

Date:  Thursday, 21 Sept. 2000
Time:  7:00 PM refreshments, 7:30 PM talk
Place: National Institute of Standards and Technology
       325 Broadway, Boulder, CO
       Room 1107


Title: Building Compact Clocks for Telecom using Vertical 
Cavity Lasers


       Dr. John Kitching
       NIST, Time and Frequency Division
       Boulder, CO



Abstract:

Synchronization is critical in wireless telecommunications 
systems for allowing the efficient transfer of data between 
network nodes. In the more sophisticated systems, 
synchronization is maintained using the Navstar Global 
Positioning System (GPS) which serves as a common reference 
timing signal broadcast to all nodes of the network. In the 
event of a temporary loss of GPS signal, however, a 
'holdover' clock is needed at each cell site to enable the 
network to operate reliably on its own for up to one day. At 
NIST, we are developing compact, low-power, inexpensive 
atomic clocks for this purpose.  These clocks use an atomic 
vapor of Cesium and new vertical cavity laser technology to 
generate a moderately stable reference frequency at 4.6 GHz. 
The timing accuracy of these devices is currently better than 
10 microseconds over one day, which meets the requirements 
set by the wireless telecom industry. I will describe our 
initial efforts at NIST to develop and engineer these compact 
devices and to understand some of the fundamental physics 
which limits their performance.

Biography: