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What is Power over Ethernet (PoE)?

February 1, 2012
What is Power over Ethernet (PoE)?

>> What is Power over Ethernet? 1. Introduction Power-over-Ethernet (PoE) or "Active Ethernet" eliminates the need to run 110/220 VAC power to Wireless Access Points and other devices on a wired LAN. Using Power-over-Ethernet system, installers need to run...
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Structured Cabling Specifications and Standards

January 19, 2012
Structured Cabling Specifications and Standards

In the past, companies often had several cabling infrastructures because no single cabling system would support all of a company’s applications. Nowadays, a standardized cabling system is important not only for consumers but also for vendors and cabling installers. Vendors...
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What is AWG (Arrayed Waveguide Grating)?

January 11, 2012
What is AWG (Arrayed Waveguide Grating)?

>> What is AWG? A remarkable device that has been made using several planar-waveguide technologies and has found a variety of applications in WDM lightwave systems is the arrayed-waveguide grating, or AWG. Arrayed-waveguide gratings (AWG) are based on the...
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What is Optical Circulator and its Applications?

January 6, 2012
What is Optical Circulator and its Applications?

>> Background History of Optical Circulator An optical circulator is a multi-port (minimum three ports) nonreciprocal passive component. The function of an optical circulator is similar to that of a microwave circulator—to transmit a lightwave from one port...
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Optical Amplifiers in Fiber Optic Communication Systems

January 3, 2012
Optical Amplifiers in Fiber Optic Communication Systems

>> A Brief Introduction to Optical Amplifiers Because fiber attenuation limits the reach of a nonamplified fiber span to approximately 200 km for bit rates in the gigabit-per-second range, wide area purely optical networks cannot exist without optical...
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What is Quantum Well Laser?

December 28, 2011
What is Quantum Well Laser?

>> The Basics of Quantum Wells Lasers Regular double heterostructure (DH) semiconductor lasers have an active region of 0.1 to 0.2um thick. Since the 1980s, lasers with very thin active regions, quantum well lasers, were being developed in many research...
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What are Dispersion Compensating Fibers?

December 15, 2011
What are Dispersion Compensating Fibers?

>> The Background In recent years there has been a lot of work on dispersion-compensating fibers (DCFs), which are being used extensively for upgrading the installed 1310nm optimized optical fiber links for operation at 1550nm. In the following two sections,...
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What is Fiber Optic Polarization Controller?

December 14, 2011
What is Fiber Optic Polarization Controller?

>> The Birefringence of Single Mode Fiber Circular core fibers whose axes are straight are not birefringent – that is, the two orthogonally polarized LP01 mode have the same effective indices. Bending such a fiber introduces stresses in the...
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What is Chromatic Dispersion ? (material dispersion and waveguide dispersion)

December 12, 2011

Chromatic dispersion is the term given to the phenomenon by which different spectral components of a pulse travel at different velocities. To understand the effect of chromatic dispersion, we must understand the significance of the...
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What is Effective Length and Effective Area ? (concepts for understanding nonlinear effect in optical fibers)

December 12, 2011
What is Effective Length and Effective Area ? (concepts for understanding nonlinear effect in optical fibers)

>> Effective Length Le The nonlinear interactions in optical fibers depends on the transmission length and the cross-sectional area of the fiber. The longer the link length, the more...
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What is a Large Effective Area Fiber?

December 9, 2011
What is a Large Effective Area Fiber?

The effect of nonlinearities can be reduced by designing a fiber with a large effective area. Non-Zero Dispersion Shifted fibers (NZ-DSF) have a small value of the chromatic dispersion in the 1550nm band to minimize the effects of...
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What are Phase Velocity, Group Velocity, and Signal Velocity?

December 9, 2011
What are Phase Velocity, Group Velocity, and Signal Velocity?

================================================================================================ Frequency dispersion in groups of gravity waves on the surface of deep water. The red dot moves with the phase velocity, and the green dots propagate with the group velocity. In this deep-water case, the...
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What is Pulse Code Modulation (PCM)?

December 7, 2011
What is Pulse Code Modulation (PCM)?

>> What is exactly PCM? Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as...
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What is Four-Wave Mixing (FWM) in Fiber Optic Communication Systems?

December 1, 2011
What is Four-Wave Mixing (FWM) in Fiber Optic Communication Systems?

>> Nonlinear Effects in High Power, High Bit Rate Fiber Optic Communication Systems When optical communication systems are operated at moderate power (a few milliwatts) and at bit rates up to about 2.5 Gb/s, they...
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Jitter and Wander Testing for Fiber Optic Systems

November 22, 2011
Jitter and Wander Testing for Fiber Optic Systems

>> What is Jitter and Wander? 1. Jitter: Jitter is the short-term phase variations of the significant instants of a digital signal from their ideal positions in time. It is the deviation of the significant instants of...
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Surface Emitting Lasers

November 21, 2011
Surface Emitting Lasers

Most semiconductor lasers have cleaved facets that form the optical cavity. The facets are perpendicular to the surface of the wafer and light is emitted parallel to the surface of the wafer. But for many applications requiring a two-dimensional laser array or...
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