INTRODUCTION FROM POINT-TO-POINT TO NETWORKING LIGHT SOURCES OPTICAL FIBERS LIGHT DETECTION NOISE IN OPTICAL COMMUNICATIONS INCOHERENT DETECTION TDMA WDMA SUBCARRIER MULTIPLEXING PHOTONIC SWITCHING SIGNAL PROCESSING DIRECT MODULATION DFB LASER DIODES AND MODULATION EXTERNAL MODULATION COHERENT DETECTION TIMING RECOVERY AND LINE CODING OPTICAL AMPLIFICATION OPTICAL FIBER SOLITON TRANSMISSION