Ch6Sec7 - THE FIBER FORUM Fiber Optic Communications...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
THE FIBER FORUM Fiber Optic Communications Dr. JOSEPH C. PALAIS PRESENTED BY
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Dr. Joseph C. Palais 6.7 2 Section 6.7 Optical Amplifiers
Background image of page 2
Dr. Joseph C. Palais 6.7 3 Design of long-distance fiber links (say > 50 km), requires repeaters or amplifiers to boost power levels. System with repeaters: Fiber Fiber Fiber Transmitter Repeater Repeater Receiver
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Dr. Joseph C. Palais 6.7 4 The repeater detects the digital optical signal, determines the presence of 0’s and 1’s and then regenerates the optical signal. Example: TAT - 8 Transatlantic fiber cable (1988) Link length ~ 5600 km Number of repeaters ~ 130 Maximum spacing ~ 50 km
Background image of page 4
Dr. Joseph C. Palais 6.7 5 Repeater properties: Costly Require large power supply Difficult to maintain Digital only Optical amplifiers solve most of these problems. How do we build an optical amplifier? We know that all lasers contain optical amplifiers. Therefore, the semiconductor LD is a possible optical amplifier, as illustrated on the next slide.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Dr. Joseph C. Palais 6.7 6 Active layer AR coating Output fiber Input fiber n P V 6.7.1 Semiconductor Optical Amplifier AR coating
Background image of page 6
Dr. Joseph C. Palais 6.7 7 Problems: 1. Low gain 2. High noise 3. Polarization dependent gain 4. Low coupling efficiency to the fiber The solution to the problems of the semiconductor amplifier is the erbium-doped-fiber amplifier (EDFA). It is illustrated on the next slide.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Dr. Joseph C. Palais 6.7 8 Fiber Fiber Transmitter EDFA Receiver G Digital signals are illustrated at the top and analog signals along the bottom of the figure.The EDFA is a practical amplifier. 6.7.2 Erbium-Doped Fiber Optical Amplifier
Background image of page 8
Dr. Joseph C. Palais 6.7 9 EDFA Components Material : Erbium-doped fiber. Erbium: A rare earth atom. It is the active material. Silica: The host material (fiber). The major points of the erbium absorption spectrum are shown on the next slide:
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Dr. Joseph C. Palais 6.7 10 980 1480 1550 λ (nm) 20 nm Amplification Pump Pump Non-radiative transitions Erbium Absorption Spectrum
Background image of page 10
6.7 11 There is a strong radiative transition from the 4I 13/2 level to the ground level, as indicated on the energy-level diagram on the next slide. The lifetime of this level is long (~10 ms). The radiation is around wavelength 1550 nm (and about 20 to 30 nm wide). There is strong absorption at 980 nm and 1480 nm
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/11/2010 for the course EEE EEE-448 taught by Professor Palais during the Fall '09 term at ASU.

Page1 / 41

Ch6Sec7 - THE FIBER FORUM Fiber Optic Communications...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online