Electro-Optics - Applied Optics Fundamentals and Device Applications - page 37

ON state

I / P

+ -

θ B

2θ B

OFF state

FIGURE 2.24
Bragg-effect electro-optic modulator.

required device lengths since the cell sizes for integrated optical devices are
quite large relative to electrical integrated circuits. Device lengths of several
millimeters are required if high modulation rates are to be achieved. Device
widths are less, however, and there is a great potential for arrays of identical
devices to be fabricated onto a single crystal of LiNbO 3 with parallel inputs.
At this time, the best lightwave system performance of 8 Gbs/s over an unre-
peatered distance of 68 km [53] is achieved via the use of Ti:LiNbO 3 devices.
As the technology matures, these devices are expected to play a critical role
in future optical signal communications.

2.4 ApplicationsofFiber-OpticSystems
Fiber-optic transmission is utilized in data communications and telecom-
munications for local area networks and telephone trunks. Video transmis-
sion, closed circuit television, cable television, and electronic news gathering
utilize fiber optics, while in the military, command, control, and communi-
cations and tactical field communication systems are being developed and
installed with fiber links. Optical circuits are applicable in each of these
applications as interconnecting components in the system. Active devices
such as sources and detectors are utilized in transmitters and receivers, and
a number of passive devices perform various critical functions in the fiber-
optic system. These functions include switching and routing, modulation,
regeneration, processing, sensing, and multiplexing. Devices include taps,
distributors, couplers, concentrators, switches, relays, multiplexers (MUXs),
cross connection cabinets, and gratings. Local area network topologies cur-
rently in use as well as those in the development stages require a number
of devices for the most efficient operation. A growing trend is toward all-
optical switching systems, eliminating the use of slower electrical routing of
information.
When comparing the performance of fiber transmission media to the alter-
native electrical twisted pair or coaxial cable conductor, the ability to utilize