Claddingpumped Fiber Lasers

The output power of EDFAs has, to date, been limited only by the amount of single-mode coupled pump power that one has available for pumping into one of the many absorption bands of erbium-doped fibers. The optical powers that are currently available from single-mode fiber-pigtailed laser diodes are on the order of 100 mW. These powers are limited by intrinsic materials properties of the laser diodes themselves (e.g., facet damage) and are not likely to be significantly improved in the next 10...

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4 X 10 20 2 X 10-31 2 X 1069 1 x 107 signal (Q factor) of a 5900-km-long 5-Gb s NRZ transmission test bed for various scrambling frequencies between 40 kHz and 10 GHz (Heismann 1995). The largest SNR improvements of more than 4 dB are obtained with high-speed scrambling at 5 and 10 GHz. where the detection of the high-speed digital data is not affected by undesired intensity modulation arising from interactions of the polarization scrambling with polarization-dependent loss in the system...

Elastic Properties Of Crystals And The Effect

Let us first consider some of the problems that exist for bulk semiconductor lasers. Although our primary concern is with quantum well structures, the physics of bulk semiconductors provides a good comparative reference. Lattice-matched direct bandgap bulk semiconductors have broad energy bands that make current injection and carrier transport possible. However, of the wide range of energy and momentum values these carriers (holes and electrons) can assume, only a very small fraction have the...

Noise Figure

The amplification of the EDFA is inescapably accompanied by a background of amplified spontaneous emission (ASE). ASE arises when light emitted by spontaneous decay of excited erbium ions is captured by the optical fiber waveguide and then amplified in the EDFA. This ASE background adds noise that degrades amplified signals. The noise figure, defined as the signal-to-noise ratio (SNR) at the output divided by that corresponding to the shot noise of the signal at the input, is a measure of the...

Gain Coefficient Spectra

1460 1480 1500 1520 1540 1560 1580 1600 Wavelength nm Fig. 2.5 Gain coefficient spectra for different values of inversion lor an erbium-doped liber with A1 and Ge co-doping. 1460 1480 1500 1520 1540 1560 1580 1600 Wavelength nm Fig. 2.5 Gain coefficient spectra for different values of inversion lor an erbium-doped liber with A1 and Ge co-doping. doping. For an amplifier, or even for a complete system, the gain divided by the total length of erbium-doped fiber determines the inversion and thus...

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Tion is that the pump spot size is decoupled from the device length. As a consequence, the high excitation density present in the single-mode core is maintained over the entire device length, which is typically several meters or even tens of meters. This leads to a high degree of flexibility in rare-earth ion concentration that is not possible in bulk up-conversion devices. This flexibility in concentration can be critical in obtaining efficient up-conversion laser operation when there are...

Performance Monitoring

In long-haul systems, the capability to remotely monitor the performance of any repeater and to locate the cause of system degradation and faults is essential. Past submarine systems were based on optoelectronic regenerative repeaters hence, each repeater had access to the data signal. The advantage that optically amplified systems have over regenerative systems whereby their operation is independent of the data stream is a disadvantage in designing a fault-detection scheme. A new supervisory...

Submarine Systems

The reliability required of undersea communications systems differentiates them from the systems developed for terrestrial applications. Repairs to undersea systems are extremely expensive and require many days to complete. Therefore, for hardware to be placed under the sea, the primary design focus is on reliability. The demand for highly reliable systems leads to a desire for simplicity, limits the complexity of designs and hence the features available, and restricts the choices available for...