Learning Center

What is the relationship between MHz and Mbps ratings of a fiber optic cable?

February 7, 2014

MHz is the frequency or rate at which a wave will cycle per second. 1 Megahertz would be equal to 10^6 Hertz or 1 million cycles per second. Mbps refers to the how many bits of data is transmitted trough a media (such as fiber optic cable) per second. MHz and Mbps are not equal, the confusion occurs because MHz works with analogue signals while a data transfer occurs digitally. Transferring data rate (Mbps) to a cable is dependent upon encoding techniques. “Manchester” encoding is used for Standard Ethernet (10 Mbps), which is a two-level encoding technique that requires a

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Modulation Formats for 100G and beyond

January 15, 2014

This article examines the options for the modulation formats for serial optical transmission of 100 Gb/s and beyond. The first part covers classical binary electronic time division multiplexed 100 Gbit/s NRZ systems, operating a highest speed, and mature product solutions of system vendors running at lower symbol rates which are using quaternary phase shift keying and polarization division multiplexing, coherent technologies and digital signal processing in the receiver. The second part covers the next generation of transmission systems carrying data at channel bitrates higher than 100 Gbit/s, e.g. 400 Gbit/s up to 1 Tbit/s or even beyond, which may apply

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What is Ethernet Auto-Negotiation?

January 9, 2014

Auto-negotiation is the feature that allows a port on a switch, router, server, or other device to communicate with the device on the other end of the link to determine the optimal duplex mode and speed for the connection. The driver then dynamically configures the interface to the values determined for the link. 1. Speed: Speed is the rate of the interface, usually listed in megabits per second (Mbps). Common Ethernet speeds include 10 Mbps, 100 Mbps, and 1,000 Mbps. 1,000 Mbps Ethernet is also referred to as Gigabit Ethernet.

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Attenuation In Optical Fibers – from Visible Light to Infrared (635nm–1625nm)

January 8, 2014

Attenuation is the reduction in optical signal (amplitude and intensity) as it propagates along a fiber. Attenuation is due to absorption, scattering and other loss mechanisms (such as impurities, bending, and coupling). Attenuation is usually expressed in dB or as a rate of loss per unit distance (dB/km). The following picture shows the three wavelength windows being used in fiber optic communications.

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

January 8, 2014

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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Fiber Optic Systems Standards and Recommendations

January 8, 2014

Here we list some of the international and national standards that govern optical cable characteristics and measurement methods. This may not be a complete list, but it covers most of the standard bodies.   :: International Standards There are two main groups that cover international standards: IEC and ITU. 1. IEC – International Electrotechnical Commission IEC is a global organization and it makes international standards that covers all electrical, electronic, and related technologies. These international standards serve as a basis for national standardization. IEC is composed of many technical committees. Each committee prepares technical documents on specific subjects. For example,

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What Are APC (Angled Physical Contact) Fiber Connectors?

January 7, 2014

:: What Are APC Connectors? APC Connector is a type of fiber connector that minimizes backreflection due to a 5° to 15° angle-polish applied to end faces. Like illustrated in the following picture. Because of the angle, the reflected light does not stay in the fiber core but instead leaks out into the cladding. Angle-polished connectors should only be mated to other angle-polished connectors. Mating to a non-angle polished connector causes very high insertion loss. Generally angle-polished connectors have higher insertion loss than good quality straight physical contact ones. “Ultra” quality connectors may achieve comparable back reflection to an angled

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What Are ASE (Amplified Spontaneous Emission) Light Sources?

January 7, 2014

:: 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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What is Corning’s SMF-28e+ LL (Low Loss) Fiber?

February 28, 2013

Corning® SMF-28e+® LL optical fiber is an ITU-T G.652.D compliant optical fiber which builds on Corning’s low loss fiber technology to enable extended networking distances for long haul, metro and access applications. SMF-28e+ LL optical fiber offers industry leading specifications for attenuation and polarization mode dispersion values which provide a solid foundation for new network deployments as well as upgrades to existing networks. :: Corning SMF-28e+ LL (Low Loss) Fiber Specifications:

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The Comparison Between Air Blown Fiber Systems and Conventional Cabled Optical Fiber Systems

February 27, 2013

:: What Is Air Blown Fiber?   Air Blow Fiber (ABF) systems claim to offer reduced cost, increased design flexibility and other advantages that cannot be matched by conventional optical fiber cables. ABF systems originated in 1982 at British Telecom. The intent of the design was to easily accommodate moves, adds, and changes with minimal disruption. The ABF system was developed to allow switching between fiber types as they evolved. ABF systems consist of a network of tube-cables installed between locations, with fiber blown into the tubes only as needed. ABF systems claim to offer cost advantages over conventional cabling

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