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Archived — Test Equipment

What is Attenuation Dead Zone (ADZ) for OTDR Testing?

Attenuation Dead Zone (ADZ) is the minimum distance for an OTDR to detect a non-reflective event (for example, splice) following a reflective event. The attenuation dead zone depends on the pulse width, the reflectance, the loss, the displayed power level and the location. The following pictures clearly illustrate one fusion splice event following a connector pair event. The first one falls within the Attenuation Dead Zone, and the second one falls out of the range of the Attenuation Dead Zone.

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What Are ASE (Amplified Spontaneous Emission) Light Sources?

:: What is ASE? ASE stands for Amplified Spontaneous Emission. Let’s explain it in two steps. 1. Spontaneous Emission Spontaneous emission is the process by which an atom, molecule or nucleus in an excited state drops to a lower-energy state, resulting in the creation of a photon. 2. How is Spontaneous Emission Amplified If the spontaneous emission happens in a gain medium, such as EDFA (Erbium Doped Fiber Amplifier), this spontaneous emission can be amplified by the process of stimulated emission as described below. Stimulated emission is the process by which, when perturbed by a photon, matter may lose energy

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Polarization Mode Dispersion (PMD) Tutorial

>> What is PMD versus Differential Group Delay (DGD)? Polarization Mode Dispersion (PMD) is the average Differential Group Delay (DGD) one expects to see when measuring an optical fiber. DGD is the time separation or delay between the two principle polarization modes of the transmission link at the receiver. DGD is an instantaneous event and varies randomly with wavelength and time. This means that DGD is a statistical parameter, obeys the law of probability theory and thus has uncertainty associated with it. PMD is the average value of a distribution of a large number of independent DGD measurements.   >>

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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 laboratories. A quantum well laser is a laser diode in which the active region of the device is so narrow that quantum confinement occurs. The wavelength of the light emitted by a quantum well laser is determined by the thickness of the active region rather than just the bandgap of the material from which it is constructed. This means that

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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 a digital signal from the ideal, equidistant values. The significant instant can be any convenient, easily identifiable point on the signal such as the rising or falling edge of a pulse. Otherwise stated, the transitions of a digital signal invariably occur either too early or too late when compared to a perfect square wave. 2. Wander: A second parameter closely related to jitter

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