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Microprocessor Controlled Fiber Optic System

IP.com Disclosure Number: IPCOM000053052D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 3 page(s) / 70K

Publishing Venue

IBM

Related People

Moore, VS: AUTHOR [+3]

Abstract

A microprocessor is actively employed in a full duplex fiber optic communication link. The microprocessor optimizes light-emitting diode (LED) drive current, thereby improving LED life and reliability. By maintaining a constant light level, the cost of the associated light receiver is substantially reduced. The microprocessor may also perform handshaking and reliability and serviceability (RAS) duties.

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Microprocessor Controlled Fiber Optic System

A microprocessor is actively employed in a full duplex fiber optic communication link. The microprocessor optimizes light-emitting diode (LED) drive current, thereby improving LED life and reliability. By maintaining a constant light level, the cost of the associated light receiver is substantially reduced. The microprocessor may also perform handshaking and reliability and serviceability (RAS) duties.

Light transmitters, commonly implemented with LEDs, are engaged in fiber- optic links as elements for sending signals down fiber-optic waveguides. These devices have lifetimes predicated on the currents which they draw based on the light which they emit. To guarantee long and proper life, this current must be carefully set so as not to exceed the proper operating levels of the LED devices. A microprocessor is useful for setting and then monitoring LED light levels to ensure that each LED emits light at its optimum lifetime level.

Fig. 1 shows a representative microprocessor-controlled fiber-optic full duplex communication unit 1, and Fig. 2 shows the link with two microprocessor- controlled units 1 and 2 interconnected by means of light waveguide 3. Unit 1 includes microprocessor controller 4, transmitter section 1a and receiver section 1b. Data In signals on line 5 from the Host computer drive current switch 6 through AND circuit 7 and OR circuit 8 under control of a Gate Data line 9. Light signals are provided to the fiber 10 from LED 11.

Received signals are derived from fiber 12 to photo-diode 13, and are directed to preamplifier 14, postamplifier 15, and to the Host by way of Data Out line 16 under control of AND circuit 17 and gate line 18. Clock signals are supplied on line 20 from AND circuit 21, also gated by line 18 and originated from phase-locked loop (PLL) block 22.

Communication begins by resetting each microprocessor controller. This action activates a start-up procedure designed to first calibrate each system. In this mode one unit is programmed to be the prime unit, i.e., the unit whose LED transmitter is to be calibrated first. The other unit serves as the slave unit. Calibration begins with the prime unit slowly and constantly increasing the drive and, hence, the light level to its LED. When the slave unit receives a pulse greater than a preset level judged sufficient for error-free communication, it signals the prime unit, which in turn establishes that level as the proper and minimum light level required by the slave. The prime and slave then change roles,...