Understanding Fiber Optic Based Light Source

Each piece of active electronics will have a variety of light sources used to transmit over the various types of fiber. The distance and bandwidth will vary with light source and quality of fiber. In most networks, fiber is used for uplink/backbone operations and connecting various buildings together on a campus. The speed and distance are a function of the core, modal bandwidth, grade of fiber and the light source, all discussed previously. Light sources of the fiber light source are offered in a variety of types. Basically there are two types of semiconductor light sources available for fiber optic communication – The LED sources and the laser sources.
Using single mode fiber for short distances can cause the receiver to be overwhelmed and an inline attenuator may be needed to introduce attenuation into the channel. With Gigabit to the desktop becoming commonplace, 10Gb/s backbones have also become more common. The SR interfaces are also becoming common in data center applications and even some desktop applications. As you can see, the higher quality fiber (or laser optimized fiber) provides for greater flexibility for a fiber plant installation. Although some variations ( 10GBase-LRM SFP+ and 10GBASE-LX4) support older grades of fiber to distances 220m or greater, the equipment is more costly. In many cases, it is less expensive to upgrade fiber than to purchase the more costly components that also carry increased maintenance costs over time.
Light sources of the fiber light source are offered in a variety of types. Basically there are two types of semiconductor light sources available for fiber optic communication – The LED sources and the laser sources.
In fiber-optics-based solution design, a bright light source such as a laser sends light through an optical fiber, called laser light source . Along the length of the fiber is an ultraviolet-light-treated region called a “fiber grating.” The grating deflects the light so that it exits perpendicularly to the length of the fiber as a long, expanding rectangle of light. This optical rectangle is then collimated by a cylindrical lens, such that the rectangle illuminates objects of interest at various distances from the source. The bright rectangle allows line scan cameras to sort products at higher speeds with improved accuracy.
The laser fiber-based light source combines all the ideal features necessary for accurate and efficient scanning: uniform, intense illumination over a rectangular region; a directional beam that avoids wasting unused light by only illuminating the rectangle; and a “cool” source that does not heat up the objects to be imaged. Currently employed light sources such as tungsten halogen lamps or arrays of light-emitting diodes lack at least one of these features.
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THE IMPORTANCE OF TESTING FIBER OPTIC END FACES

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To make sure that the fiber optic cables in your fiber optic network are working properly at all times, it’s important for you to inspect, test, and clean your fiber optic end faces on a regular basis. If you don’t do this, your fiber optic end faces can get contaminated, which can eventually lead to fiber link failure if you’re not careful. You can avoid this by taking a good, long look at your fiber optic end faces to decrease the chances of them facing contamination.
DEFECTS FOUND WHEN INSPECTING FIBER OPTIC END FACES
There are all kinds of defects that you can find when inspecting fiber optic end faces. In some cases, you’ll see dirt, dust, oil, and other debris built up on them. In others, you’ll find that cracks, scratches, and even pits have done damage to your fiber optic end faces. The good news is that, more often than not, you can use special wipes containing a solvent created to clean fiber optics to get your fiber optic end faces clean. But the bad news is that there are certain scratches that can shut your fiber optics down and prevent them from performing as well as they should.
By running tests on your fiber optic end faces, you can see which ones pass an inspection and which don’t. The fiber optic end faces that pass can be used like normal moving forward. However, the fiber optic end faces that fail will either need to be repaired or replaced to bring them back up to speed. Many pits and cracks can be fixed by an experienced fiber optic company. But larger scratches in the wrong location could doom fiber optic end faces. You’ll likely need to have replacement done before you start using your fiber optics again.

Comparing Fiber Optic vs. Cable Internet

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If you’re wondering whether fiber or cable internet are right for you, here’s a quick breakdown of how both services line up across a few main areas of consideration.
Are There Differences in Speed?
At their peak, cable internet download speeds range up to about 300 megabits per second (Mbps), and upload speeds fall much lower than that. However, cable internet shares bandwidth among all customers within the same service area, so users may see a reduction in speed during busy hours.
The laws of physics mean that fiber-optic cable wins hands-down in terms of speed. Download speeds for fiber-optic internet can clock in up to 1,000 Mbps, with upload speeds that far surpass those of cable. Although fiber-optic cables don’t send data at the speed of light, they are only about one-third slower. Comparatively, the electrons in copper wire travel much slower than the light particles in fiber.
In terms of internet bandwidth, single-mode fiber is unlimited while multi-mode optical fiber has a more limited capacity to carry information. But both single-mode or multi-mode optical fiber have a clear advantage over copper cable when it comes to speed and bandwidth.
What does all that mean? Simply that the faster speeds afforded by fiber mean it’s easier and smoother to perform data-heavy tasks like video streaming or file uploading. However, for moderate data use, cable internet is still a solid option.
Which Internet Medium Is More Reliable?
Cable internet is a reliable medium that doesn’t drop out during bad weather like satellite communications. Copper wire is susceptible to electromagnetic interference and variations in temperature, though, which means customers might experience interruptions or outages in their internet.
Since glass doesn’t conduct electricity, optical fiber isn’t susceptible to those issues. Lightning damage or interruptions from high-voltage electrical equipment won’t disrupt internet connections transmitting via fiber-optic cabling.
Furthermore, while coaxial cable internet connection can lose speed and quality over long distances, fiber optic cable still provides speedy, reliable transmission of data even over great lengths.
Are They Equally Available Everywhere?
Copper cable has been a communications standard for decades, and with 89% coverage nationally, it has an edge in terms of internet availability.
Access to fiber-optic internet service, on the other hand, is growing rapidly. As availability and installation of new light-carrying fiber optic cabling expands to more areas, it is worthwhile to check what is available in your area.
What’s the Most Economic Choice?
Because copper cable networks already cover a good portion of the United States, it’s generally easy to set up a reliable internet connection that transmits internet data at an acceptable speed for an affordable monthly price. Plans vary widely, but you can find offerings under $100 in most areas.
Fiber optic internet plans can cost slightly more and possibly additional installation costs to support equipment but you will gain higher reliability and speed.
What’s the Future of Internet Connectivity?
There are multiple players in the marketplace for internet service. The industry is moving in the direction of internet technology that offers high speeds and increased reliability like fiber optics. Cable can provide adequate speed for standard internet usage, but it may be worth upgrading if fiber is available near you.
Watch for the next two articles in this series to learn more about fiber optic vs. wireless internet and fiber optic vs. DSL internet. Once you’ve done the research, you can check out Frontier Business internet services in your area to select which will best meet your needs.

Understanding Loss in Fiber Optic & How to Reduce It ?

Fiber optic cable, which is lighter, smaller and more flexible than copper, can transmit signals with faster speed over longer distance. However, many factors can influence the performance of fiber optic transmission. Losses in optical fiber are negligible issues among them, and it has been a top priority for every engineer to work with and figure out solutions for.

Light traveling in an optical fiber loses power over distance. The loss of power depends on the wavelength of the light and on the propagating material. For silica glass, the shorter wavelengths are attenuated the most (see Fig. 1). The lowest loss occurs at the 1550-nm wavelength, which is commonly used for long-distance transmissions.

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Transmission of light by fibre optics is not 100% efficient. There are several reasons for this including absorption by the core and cladding (caused by the presence of impurities) and the leaking of light from of the cladding. When light reflects off the cladding /core interface it actually travels for a short distance within the cladding before being reflected back. This leads to attenuation (signal reduction) by up to 2db/Km for a multi-mode fibre. For example, with this level of attenuation, if light travelled over 10kM of cable only 10% of the signal would arrive at the following end.

The amount of attenuation for a given cable is also wavelength dependent. Figure 1 shows the attenuation profile for the two main types of fibre; multi-mode and single-mode cable (described in detail below). The absorption peak at 1000nm is caused by the peculiarities of single mode fibre while the peak at 1400nm is caused by traces of water remaining in the fibre as an impurity. Due to this water absorption peak there are two standard single-mode wavelengths in use, 1310nm and 1550nm. 1310nm has been a standard for many years, only now is there a trend towards using 1550nm brought about by the need to extend the distances between repeaters.

The loss of power in light in an optical fiber is measured in decibels (dB). Fiber optic cable specifications express cable loss as attenuation per 1-km length as dB/km. This value is multiplied by the total length of the optical fiber in kilometers to determine the fiber’s total loss in dB.

Optical fiber light loss is caused by a number of factors that can be categorized into extrinsic and intrinsic losses:

  • Extrinsic
  • Bending loss
  • Splice and connector loss
  • Intrinsic
  • Loss inherent to fiber
  • Loss resulting from fiber fabrication

1

Figure 1. Optical fiber operating wavelengths.

  • Fresnel reflection

Bend Loss. Bend loss occurs at fiber cable bends that are tighter than the cable’s minimum bend radius. Bending loss can also occur on a smaller scale from such factors as:

  • Sharp curves of thefiber core
  • Displacements of a few millimeters or less, caused by buffer or jacket imperfections
  • Poor installation practice

This light power loss, called microbending, can add up to a significant amount over a long distance.

Splice and Connector Loss. Splice loss occurs at all splice locations. Mechanical splices usually have the highest loss, commonly ranging from 0.2 to over 1.0 dB, depending on the type of splice. Fusion splices have lower losses, usually less than 0.1 dB. A loss of 0.05 dB or less is usually achieved with good equipment and an experienced splicing crew. High loss can be attributed to a number of factors, including:

  • Poor cleave
  • Misalignment of fiber cores
  • An air gap
  • Contamination
  • Index-of-refraction mismatch
  • Core diameter mismatch to name just a few.

Losses at fiber optic connectors commonly range from 0.25 to over 1.5 dB and depend greatly on the type of connector used. Other factors that contribute to the connection loss include:

  • Dirt or contaminants on the connector (very common)
  • Improper connector installation
  • A damaged connector face
  • Poor scribe (cleave)
  • Mismatched fiber cores
  • Misaligned fiber cores
  • Index-of-refraction mismatch

Loss Inherent to Fiber. Light loss in a fiber that cannot be eliminated during the fabrication process is due to impurities in the glass and the absorption of light at the molecular level. Loss of light due to variations in optical density, composition, and molecular structure is called Rayleigh scattering. Rays of light encountering these variations and impurities are scattered in many directions and lost.

The absorption of light at the molecular level in a fiber is mainly due to contaminants in glass such as water molecules (OH-). The ingress of OUT molecules into an optical fiber is one of the main factors contributing to the fiber’s increased attenuation in aging. Silica glass’s (Si02) molecular resonance absorption also contributes to some light loss.

Figure 1 shows the net attenuation of a silica glass fiber and the three fiber operating windows at 850, 1310, and 1550 nm. For long-distance transmissions, 1310- or 1550-nm windows are used. The 1550-nm window has slightly less attenuation than 1310 nm. The 850-nm communication is common in shorter-distance, lower-cost installations.

Loss Resulting from Fiber Fabrication. Irregularities during the manufacturing process can result in the loss of light rays. For example, a 0.1 percent change in the core diameter can result in a 10-dB loss per kilometer. Precision tolerance must be maintained throughout the manufacturing of the fiber to minimize losses.

Fresnel Reflection. Fresnel reflection occurs at any medium boundary where the refractive index changes, causing a portion of the incident light ray to be reflected back into the first medium. The fiber end is a good example of this occurrence. Light, traveling from air to the fiber core, is refracted into the core. However, some of the light, about 4 percent, is reflected back into the air. The amount being reflected can be estimated using the following formula:

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At a fiber connector, the light reflected back can easily be seen with an optical time domain reflectometer (OTDR) trace. It appears as a large upward spike in the trace. This reflected light can cause problems if a laser is used and should be kept to a minimum.

The reflected light power can be reduced by using better connectors. Connectors with the “PC” (Physical Contact) or “APC” (Angle Physical Contact) designations are designed to minimize this reflection.

How to Reduce Losses in Optical Fiber?

In order to ensure the output power can be within the sensitivity of the receiver and leave enough margin for the performance degradation with the time, it is an essential issue to reduce the losses in optical fiber. Here are some common approaches in fiber link design and installation.

  • Make sure to adapt the high-quality cables with same properties as much as possible.
  • Choose qualified connectors as much as possible. Make sure that the insertion loss should be lower than 0.3dB and the additional loss should be lower than 0.2dB.
  • Try to use the entire disc to configure (single disc more than 500 meters) in order to minimize the number of joints.
  • During splicing, strictly follow the processing and environment requirements.
  • The connecting joints must have excellent patch and closed coupling so that can prevent the light leakage.
  • Make sure of the cleanliness of the connectors.
  • Choose the best route and methods to lay the fiber cables during design the construction.
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  • Select and form a qualified construction team to guarantee the quality of the construction.
  • Strengthen the protection work, especially lightning protection, electrical protection, anti-corrosion and anti mechanical damage.
  • Use high quality heat-shrinkable tube.

Summary

When it comes to high-quality fiber patch cables that help in reducing losses in optical fiber, Fiber-Mart offers bend insensitive fiber (BIF) patch cables with ultra low insertion loss (IL) and bend radius, ensuring high performance of data transmission.I believe you can find a suitable fiber optic patch cable for your devices in Fiber-Mart.please contact us: product@fiber-mart.com.