Page 470 - Tunable Lasers Handbook

430 Paul Zorabedian

FIGURE 49 Eutended-cavity laser module with free-space output based on commercial laser
diode package without back-facet access. (Reproduced aith permission from Wieman and Hollberg
[i7] and the American Institute of Physics. j

the instrument chassis using soft rubber spacers to reduce mechanical stress.
Together with the mainframe, the design forms a two-stage shock absorbing sys-
tem. As a result, the unit is able to withstand use in both laboratory and produc-
tion environments without special handling. The overall dimensions are
425 x 132 x 497 mm. of which the optical block takes one-third of the volume.
The remainder contains printed circuit cards and the power supply.

18. APPLICATIONS

18.1 Lightwave Communications
18. 7. 7 Coherent (Optical Heterodyne) Systems
A number of different modulation schemes fall under the heading of "coher-
ent," that is, optical heterodyne or homodyne transmission. Two of the most
widely used coherent transmission methods are phase-shift keying (PSK) and
frequency-shift keying (FSK). The spectral performance required of the optical