Fiber Optic Components

Fiber optic components are key to a fiber system’s functionality. Without them, light signals can’t be sent or received.

Optical fibers consist of a central core and a cladding. The cladding typically has a slightly lower (by about 1%) refractive index than the core. This causes total internal reflection to occur along the length of the fiber.

Core

A core is a crucial component in the fiber optic cable. It is where the light enters and exits, allowing for data transmission over long distances. It is also where the light is protected from outside damage.

There are many types of cores, but the most common are multimode and single-mode. Both have different applications and features.

In contrast to copper wiring, which is used to send signals over long distances, fiber optic cables are able to carry a higher amount of bandwidth. This allows them to support bandwidth-intensive devices, such as VoIP phones or IP cameras.

Plastic optical fiber (POF) is an inexpensive alternative to glass fibers that can be incorporated into various applications. It has a low loss, so it can be used to send signals at lower frequencies.

These fibers are usually used in applications that don’t require high bandwidth over long distances, like desktop LAN connections. They are also a great choice for extending existing networks.

However, POF has disadvantages, such as high loss and high cost. This is why many people prefer to use glass fibers in more high-demand applications.

Another disadvantage of plastic optical fibers is that they are not available in large diameters. In addition, they are less durable than glass fibers and often don’t meet quality standards.

Optical fibers can also be made using a combination of different materials. For example, one could make a plastic optical fiber that contains a silica glass core. The silica glass core acts as the light’s guiding mechanism, while the plastic optical fiber acts as its transmitting path.

These fibers can be fabricated in a variety of sizes, including 9 um, 50 um and 62.5 um. They are used in different Fiber Optic Components types of fiber cables, such as OM1, OM2, OM3 and OM4.

A multimode fiber has a relatively large core, which allows multiple frequencies of light to travel down the cable’s length. The core can also contain a cladding that prevents the light from escaping, resulting in complete internal refraction/reflection. This is the reason why many power companies choose to use fiber optic cable for their power transmission and monitoring systems.

Cladding

Fiber optics are used in many applications, including telecommunications, computer networking, and remote sensing. They transmit light signals with a process known as total internal reflection. These rays bounce off the core and cladding in a series of zig-zags until they reach the end of the glass strand, where they are converted to electrical signals by a receiver.

The cladding of an optical fiber is made from a low-refractive index material that keeps light from penetrating the core to avoid the phenomenon of total internal reflection (TIR). The cladding also helps protect the fiber against moisture and physical damage, like nicks, bumps, abrasions, and microscopic bends.

Another important part of an optical fiber’s cladding is its coating. A polymer coating is applied to the surface of the cladding to enhance its mechanical and environmental properties as well as its optical performance. There are several types of coatings, including acrylate, silicone, carbon, and polyimide.

Acrylate is the most common type of coating on a fiber. It has a soft layer that acts as a cushion for the fiber when bent and a hard outer coating that provides abrasion resistance. It can be applied in a two-layer system with the primary coating atop the cladding and a secondary coating atop the primary coating.

Step-index fibers use a uniform refractive index right up to the cladding interface, and then the index changes in a step-like fashion so that different modes of light travel along various paths down the core. Modal dispersion is a significant problem when multiple modes travel through a single core, so step-index fibers are limited in terms of speed and distance.

Graded index (GI) multimode fiber uses variations in the composition of the core and cladding to minimize modal dispersion, and thus offers hundreds of times more bandwidth than step-index fiber. GI multimode fiber is typically 50 or 62.5 microns in diameter and comes in both single-mode and multimode varieties.

Coatings are applied to the cladding of an optical fiber to help it perform optimally in the environments and conditions where it will be placed, such as industrial, military, medical, or aerospace. Some coatings are formulated to resist UV radiation, corrosive gases, and dust particles. Others are designed for high temperature applications, such as those found in mining or oil and gas drilling.

Coating

Fiber optic components are made from a thin strand of glass with an outer coating, which is important for preventing damage to the glass cladding. The coating protects the strand against moisture, air, nicks, bumps, and other hazards that can cause the cladding to crack.

The coating can also help to reduce the amount of loss in the light signal transmitted through the core of the fiber. This loss, known as microbending, can add up to a significant amount over long distances; for example, a 0.1% change in the core diameter of a multi-mode fiber can result in a 10 dB loss per kilometer.

There are many different types of coatings used on optical fibers. The most common type is acrylate, which is usually applied in two layers, with the secondary layer harder than the primary. This gives the strand a hard surface that is better for handling, and it also resists delamination.

Other kinds of coatings are designed to meet specific environmental, optical, or mechanical performance requirements. For example, silicone is a good choice for applications in harsh environments like aircraft and space. Carbon or polyimide Fiber Optic Components coatings are good for applications that require high strength.

Another type of coating is called “index matching,” which is used to minimize reflected signal at the boundaries of the connector or splice. This material can be a liquid or cement that is cured into the surface of the fiber, or it may be a gel that is injected into the connector or splice.

These coatings are usually cured with UV lamps, and they vary according to the type of application and environment. For example, silicone coatings are a good choice for harsh environments, while carbon coatings are best for oil and gas drilling applications.

Coatings are also used for a variety of other purposes, including protecting fiber ends from bending or damaging when removing them during connector and splice procedures. This is important because a bad end surface can ruin the signal quality. The ends of a fiber can be polished to improve the end face quality, or they can be cut with a precision fiber cleaver.

Photodetector

The photodetector is the main component of a fiber optic receiver, which converts light into electricity and uses this electrical signal to transmit data in an optical communication system. Generally, two types of photodetectors are used for this purpose: p-n photodiodes and avalanche photodiodes.

The p-n photodiode is a semiconductor device with a p-n junction (i = intrinsic material). This type of photodetector can be compact, highly linear, and have a high quantum efficiency. However, it is not as sensitive as a p-i-n photodiode. In addition, this type of photodiode may suffer from a significant level of dark current that sets a floor on the minimum detectable signal.

Alternatively, a p-i-n photodiode has an i-region that absorbs incoming light in a depletion region. This i-region is typically wide, which means that a larger percentage of the incoming photons will be absorbed in this region than in the p or n regions. This is a significant advantage because it allows for faster response times.

A p-i-n photodiode can be fabricated in a variety of semiconductor materials. These include silicon, Germanium, and Indium Gallium Arsenide (InGaAs).

When using a photodetector, the sensitivity of the device can be measured in terms of its quantum efficiency and responsivity. Quantum efficiency refers to the probability that one electron-hole pair is emitted from the device after each absorbed photon, while responsivity measures how sensitive the photodetector is to an optical input signal.

Sensitivity is an important design parameter for many applications. It can be expressed as a fraction of the noise-equivalent power, or NEP, which is the minimum optical power that can generate photocurrent. NEP is a function of frequency, bandwidth, and detector area, as well as operating temperature.

The EM169 photodetector offers bandwidth rated to a minimum of 20 GHz over the 1280-1620 nm wavelength range and can handle 3 mW (5 dBm) average power and 6 mW (8 dBm) absolute maximum power, with typical responsivity of 0.95 A/W. The EM169 also has a high noise-equivalent power and can provide more than 500 mA of photocurrent when detecting an input light pulse of 50 mW.