ating 250 um to Mode Field Diameter (the Near-Field Method) 1.4-2.0 mm 900 um diameter 500 um Diameter Diameter A small area detector is used to scan the magnified image a) Tight Buffered b) Loose Tube of the fiber end (Fig. 6.1-19). The experimental data are fitted to Eq. (6.1.10), from which the mode-field Fig. 6.1-22 Common single-fiber cable types. Reprinted from diameter can be calculated. Ref. [1], p. 36, courtesy of Academic Press. CHAPTER 6.1 Optical fiber, cable and connectors OUTER JACKET CORRUGATED ARMOR INNER JACKET SOLID FILLER OPTICAL FIBERS KEVLAR RIPCORD TAPE WRAP GEL-FILLED PRIMARY TUBE STRENGTH MEMBER JACKET CENTRAL STRENGTH MEMBER Fig. 6.1-23 Fiber optic cable-corrugated armor. Reprinted from Ref. [21], p. 247, courtesy of Academic Press. TO can Packaged diode laser mounted in a TO-5 header can includes a PIN photodiode to monitor the beam output and a heat sink to reduce the effects of temperature instabilities. LASER DIODE PKG Glass SELFOC LENS window Heat sink Laser chip Monitor photodiode FERRULE STOP MODULE RX IC OTOSA DESERIALIZER TX IC CLK REC CHIP SERIALIZER Fig. 6.1-24 Common solution today; Laser TO can -> optical subassembly (OSA) -> module. There are three levels of packaging and several active alignments. Reprinted from Ref. [22], p. 134, courtesy of Academic Press. Optical fiber, cable and connectors CHAPTER 6.1 ST SERIES CONNECTOR LOCKING NUT ALIGNMENT SLEEVE THREADED COUPLING HOUSING Fig. 6.1-25 Straight tip ferrule single fiber connector. Reprinted from Ref. [23], p. 303, courtesy of Academic Press. In the second measurement an additional loop with di- arc lamp and a typical delay curve is shown in ameter 4-6 cm is used to, as much as possible, attenuate Fig. 6.1-21. the higher order modes. The cutoff is then defined as the wavelength for which the normalized power becomes linear to within 0.1 dB (Fig. 6.1-20). 6.1.3 Cable designs Chromatic dispersion (interferometric Because an optical fiber is very brittle and susceptible to method) chemical degradation it is important to pro