itters emit light only in the infrared spectrum. The difference in performance of the various wavelengths is beyond the scope of this paper. What is important is an awareness of the wavelengths and that the equipment on both ends of the fiber needs to be matched. The final characteristic of transmitters is the output power. This is a measure of the optical energy (intensity) launched into the fiber. It is measured in dBm. A typical value for multi mode transmitters used in Ethernet is -15dBm. Single mode transmitters have a wide range in power depending on the application.Receiver Specifications With a knowledge of transmitters, what happens at the other end of the cable is important. The light pulses are terminated and detected with a receiver. Receivers have three basic considerations. These are: 1.wavelength 2.mode (single vs. multi) 3.sensitivity Sensitivity is the counterpart to power for transmitters. It is a measurement of how much light is required to accurately detect and decode the data in light stream. It is expressed in dBm and is a negative number. The smaller the number (remember -40 is smaller than -30) the better the receiver. Typical values range from -30dBm to -40dBm. Receive sensitivity and transmitter power are used to calculate the optical power budget available for the cable. This calculation is: Power Budget = Transmitter Power - Receiver Sensitivity, Using the typical values given for multi mode Ethernet above, the power budget would be: 15dBm = -15dBm - (-30dBm) The optical power budget must be greater then all of the cable plant losses (such as attenuation, losses due to splices and connectors, etc.) for the installation to work properly.Connector TypesFigure A. - SC Connector Figure B. - ST Connector Many different connector styles have found their way into fiber optic networking. The SC connector (Figure A) has recently been standardized by ANSI TIA/EIA-568A for use in structured wiring insta...
