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What Is the Working Principle of Fiber Optic Cables

For understanding the working principle of optical fiber cable clearly, we first further learn the components of an optical fiber cable.

Components of Fiber Cable

A fiber optic cable can be divided into three parts. It is a coaxial cable, and the center most part is called the core which is made out of a very clear glass tube and carries the information. The plastic covering above it which causes the reflection of light signals is called the cladding and the sheathing that protects the optical fiber is called the coating. In a single mode fiber, the core is about 5-10 microns in diameter. A dimension of 5 to 10 microns is equivalent to the millionth of a meter. That small is the core of an optical fiber.

The reason why core is made out of glass is that, glass is incredibly pure so that, even though it is several miles long, light can still make it through. The glass is drawn into a very thin strand, with a thickness comparable to that of a human hair. The glass strand is then coated in two layers of plastic. So fiber optic cable is also called glass fiber cable.

In order for the finished cable to transmit data signals, it needs to be connected to the three other main components of a fiber optic system, named optical transmitter, optical receiver and optical regenerator.

Optical Transmitter

Optical transmitter, a device which converts electrical and analog signals into either On-Off or Linear modulating light signals, then releases that data into the fiber optic cable. The pattern of light waves forms a code that carries a message. The cable then relays the data emitted by the optical transmitter to the optical receiver, which accepts the light signal and reformats the data into its original form.

Optical Receiver

The receiver is essentially performing the opposite function of the transmitter. Optical receivers receive the light signal from the fiber optic able and turn it back into information that a computer or television know how to understand and use. It then sends the decoded signal to the computer or television.

Optical Regenerator

Sometimes a light signal must travel through a fiber optic cable over a very long distance. Although signal degradation is minimal in a fiber optic patch cable, some degradation does occur. When a cable covers a long distance, optical regenerators are placed at certain intervals along the cable. Optical regenerators are fibers that have been treated with a laser. The molecules in the fiber allow the signal traveling through the fiber optic cable to take on laser properties themselves, which strengthens the light signal. Optical regenerators essentially strengthen the light signal that is traveling through a fiber optic cable.

Working Principle of Fiber Optic Cable

The light travels through the glass strands and continuously reflects off of the inside of the mirrored plastic coatings in a process known as “Total Internal Reflection”.

When light travels from a medium of lower refractive index to that of a higher refractive index, it bends towards the normal. The normal is a line that is perpendicular to the interface of two mediums. However, when light travels from a medium of higher refractive index to that of a lower refractive index, it bends away from the normal.

The angle made by the incident ray to the normal is called the angle of incidence and the angle made by the refracted ray with the normal at the point of incidence in the other medium is called the angle of refraction. Now, consider that light is traveling from a medium with higher refractive index to that of a lower refractive index. As the angle of incidence increases, the angle of refraction also increases. Now, if the angle of incidence is increased to a point that the angle of refraction becomes perpendicular to the angle of refraction, almost parallel to the interface of the two media, then this particular of angle of incidence is called the critical angle. If the angle of incidence is further increased beyond this angle of incidence, then the refracted light will be returned to the same medium, reflected. This is the process of total internal refraction.

What happens in fiber optics is that the light is sent at such an angle almost parallel to the optical fiber, it goes through the process of total internal reflection and travels through hundreds of kilometers. Besides, as we all know that the highest speed of any form of energy is that of light energy. So, it has to be the fastest way of communication. Light gets reflected at the walls of the pure glass and hence travels through hundreds of kilometers.

In order for optical fibers to transmit data over long distances, they need to be highly reflective. On their way to being spooled, newly-pulled glass fibers pass through coating cups and ultraviolet ovens, which respectively apply and then cure the thin plastic buffer coating that creates a mirror effect within the fiber.

The typical three types of fiber optic cables, including multimode fiber optic cable, single mode cable and plastic optical fiber cable (POF), are all adaptable to the basic structure and working principle.

Fiber Optic Connectors in FTTD Applications

Because of major national policy support, to develop the field of fiber optic products, optical fiber gradual decline in the price of the cost, fiber optic installation and construction are also increasingly simple and convenient, plus high-bandwidth optical fiber, a wide range of applications, from external electromagnetic interference and prevent signal leakage, etc., fiber optic system solutions increasingly factored by customers. FTTx is the use of optical fiber as a transmission channel network physical layer information media, mainly as a network of broadband access. x represent different scenarios applications generally include the following:

1. FTTC (Fiber to The Curb/Cell) is mainly for residential service, ONU telecommunications equipment installed in the side of the road junction box, through the coaxial cable extending from ONU transmission CATV signal, twisted-pair copper networks to transmit voice and fiber optic splice mode signal.

2. FTTB (fiber to the building) service object has two types, one is an apartment building home users, the other is the commercial building companies or business units. ONU devices are generally placed on the bottom into a building (such as the basement), where apartment buildings may be FTTC ONU extension; while commercial buildings because it is a company or business office services enterprises, so that the network transmission performance requirements are higher, network stability and security requirements more stringent.

3. FFTH (Fiber to The Home) optical fiber directly extended to all home users, all-digital network services, to provide users with a variety of life and entertainment services, such as a doctor at home, online shopping, video on demand, remote training.

4. FTTD (fiber to the desk) refers to the fiber completely replace the traditional copper twisted-pair transmission medium extends directly to the user terminal (such as office computers, printers, etc.), the user terminal to achieve full network access through fiber, improves network transmission bandwidth, extending the transmission distance, and enhance the stability of the network and information security.

The main impact of the test fiber system performance parameters – decay, in addition to the quality of their products with the relevant cable, the most important is the construction and installation process.

1. Fiber polishing method: through on-site hand-grinding, with epoxy adhesive curing, the connector assembly steps to complete the cable connection. Now the basic fiber polishing method should not be adopted, because this way the construction workers demanding technical level, and for the present single-mode systems, Gigabit multimode networks, grinding mode is difficult to achieve, unstable performance.

2. Fiber splicing method: it works by fiber alignment system to align the ends of optical fibers, the use of high-temperature high-pressure arc discharge tip of the principle and performance of fiber-optic high temperature melting, so that fiber splicing together to obtain low loss, low reflection fiber optic fusion splice. Fiber splicing method most widely used at this stage, the most suitable for application in a large number of relatively concentrated fiber termination, especially in the wiring between the application of the cabinet.

3. Fiber Optic Splice method (also called mechanical fiber splice): The whole process does not require cold then hot welding machine, suitable for relatively small number of core optical fibers, optical fiber connecting geographically dispersed, especially suitable for the application in the FTTD.

Fast optical fiber connector is characterized by the application FTTD

Fast fiber optic connectorsis smaller than the volume of the common connector smaller, more convenient wall and desktop installation, to ensure the stability of the optical system performance and reliability. However, if the conventional optical fiber splicing manner, since the heat-shrinkable sleeve has a length 6 ~ 7mm, the bottom panel 86 of the cartridge mounting space is not deep enough, it cannot guarantee performance of the fiber splice and fiber bend radius requirements may result network communication is unstable.

Fast fiber optic connector with fiber embedded in the factory, without gluing and sanding, simple and convenient. Process does not require the entire cold then hot melt machine, greatly reducing the complexity of fiber termination, saving fiber splice time and improve the efficiency of construction.

Fast fiber optic connector with a simple construction and installation requires only a crimping tool to completer fiber optic splice, easy to use and short training period; and cold connection equipment investment cost is small, as FTTD solutions to improve the cost-effectiveness.

Fast fiber optic connector construction process does not require an active device, suitable for office construction for harsh environments, especially in pre-construction project, most of them are not powered site environment or to take power inconvenient places.

Fast fiber optic connector can be repeated production, improve the utilization of fiber head, significant cost savings.

Fast fiber optic connector is available in SC and LC connectors, multi-mode OM2, OM3 and singlemode OS2 Gigabit systems to choose from.

Guide to Fiber Optic Attenuator

Fiber Optic Attenuator is a device to reduce the optical fiber power at a certain level by a predetermined factor. The intensity of the signal is described in decibels (dB) over a specific distance the signal travels. Attenuator provides a certain amount of isolation between instruments, thus reducing measurement interaction. This can be done by attenuating the unwanted reflected signal due to imperfect matching. Fiber optic attenuators are used in applications where the optical signal is too strong and needs to be reduced, it is mainly used for fiber optic system of measurement, signal attenuation for short distance communication system and system test, etc. For example, in a multi-wavelength fiber optic system, you need to equalize the optical channel strength so that all the channels have similar power levels. This means to reduce stronger channels’ powers to match lower power channels.

The basic types of optical attenuators are fixed and Variable Attenuators. The most commonly used type is female to male plug type fiber optic attenuator, it has the fiber connector at one side and the other side is a female type fiber optic adapter. Female to male mechanical attenuator is assembled with a fixed type connector, so it can only be connected with one patch cord, such as LC Attenuator, sc Attenuator, fc Attenuator, st Attenuator, etc.

Fixed Attenuators

Fixed value attenuators have fixed values that are specified in decibels. Just its name implies, fixed value attenuator’s attenuation value cannot be varied. The attenuation is expressed in dB. The operating wavelength for optic attenuators should be specified for the rated attenuation, because optic attenuation of a material varies with wavelength. Their applications consist of telecommunication networks, optic fiber test facility, Local Area Network(Lan) and Catv systems.

Fixed value attenuators are composed of two big groups: In-line type and connector type. In-line type looks like a plain fiber patch cable; it has a fiber cable terminated with two connectors which you can specify types. The in-line fiber optic attenuator is fit to use with optical patch cables. To use these in-line Fiber Optics Attenuators just select the connector type you need ST, SC, LC, & FC Available, the Polish (PC, UPC or APC angled Polish) & the Decibel dB rating.

Variable Attenuators

Variable attenuators come with variety separate designs. They are normal used for testing and measurement, but they also have a wide usage in Edfas for equalizing the light power among separate channels. One type of changeable attenuator is built on a D-shaped fiber as a type of evanescent field device. If a bulk external material, whose refractive index is greater than the mode effective index, replaces a part of the evanescent field reachable cladding, the mode can come to be leaky and some of the optic power can be radiated. If the index of the external material can be changed with a controllable mean, straight through the effects such as thermo-optic, electro-optic, or acoustic-optic, a gadget with controllable attenuation is achievable. Other types of variable attenuators consist of air gap, clip-on, 3-step and more.

As it comes to getting a fiber optic attenuator you have several options listed above, so before you buy one you must be sure at what level you want to attenuate your signal and then choose what type will work best for you. Taking the time to choose the right one can save you big time.

LC Connector and LC Attenuator

A fiber optic connector terminates the end of an optical fiber and enables quicker connection and disconnection than splicing. The fibers are mechanically coupled and aligned to ensure that light can pass.

There has been many different connectors introduced through the development of fiber optic components previously many years. A lot of companies and individuals happen to be trying to improve the options that come with certain connectors to be able to gain control of the fiber optic industry, but only few have been successful. As technology increases, various fiber optic components have become less expensive.

There are various color codes for connectors and they have changed throughout the years. In early stages of fiber optic history, orange, black or grey represented multimode connectors and yellow represented single mode. These original codes became complicated with the introduction of metallic connectors so colored boots were developed, like FC and ST. Now, beige boots stand for multimode, blue means single mode and APC or angled connectors are represented by green boots.

The LC connector is a universal connector. It is available in simplex and duplex configurations and is half how big the SC and utilizes a 1.25mm ferule. The LC is highly favored for single mode and is easily terminated with an adhesive. They’re actively replacing the SC connectors in corporate environments due to their smaller size.

Built on style with LC, LC attenuators really are a combination of a connector on a definite end, as well as an adapter on the other. This enables so that it is “plugged-in” to just about any LC adapter. The assembly contains a ferrule that’s accessible in standard Polish connectors (PC) and 8 degree angle Polish (APC). They’re backward suitable for existing transmission equipment, while the APC attenuators provide superior reflection required for high power and analog equipment. LC fiber optic attenuators are designed to provide horizontal spectral attenuation over the full spectrum vary from 1280nm to 1624nm. This way the LC attenuators expand the capability of optical networks by enabling using the E-band (1400-nm window) for optical transmission.

LC fiber optic attenuator is a passive device accustomed to reduce light signal intensity without significantly changing the waveform itself. It provides a type of metal-ion doped fiber which reduces the noiseless signal because it passes through. This process of attenuation allows for higher performance than fiber splices or fiber offsets or fiber clearance, which function by misdirecting rather than absorbing the joyful signal. This is often a requirement in Dense Wave Division Multiplexing (DWDM) and Erbium Doped Fiber Amplifier (EDFA) applications in which the receiver can’t accept the signal produced by a high-power light source.

LC fiber optic attenuators are key in controlling manipulating the electricity of an optical path in fiber optic telecommunication systems. LC Build-on fiber optic attenuators are used to reduce excess optical power from the transmitter that can result in over-saturation of the receiver.

These optical attenuators feature simple and rugged structure utilizing ion doped fiber because the attenuating material. They can be placed directly on the active equipment and therefore are able to withstand over 1W of extraordinary power light exposure for longer periods of time, which makes them well-suited to EDFA and other high-power applications.

Relationship Between the Coupler and Splitter

Relationship between the coupler and splitter: In fact, splitter is named for the function of the device, coupler named for its working principle, splitter may be based coupler, and may be based on the waveguide or the separating element, coupler can be done either the splitter, but also can be done WDM, attenuator.

Couplers:

Fiber optic couplers either split optical signals into multiple paths or combine multiple signals on one path. Optical signals are more complex than electrical signals, making optical couplers trickier to design than their electrical counterparts. Like electrical currents, a flow of signal carriers, in this case photons, comprise the optical signal. However, an optical signal does not flow through the receiver to the ground. Rather, at the receiver, a detector absorbs the signal flow. Multiple receivers, connected in a series, would receive no signal past the first receiver which would absorb the entire signal. Thus, multiple parallel optical output ports must divide the signal between the ports, reducing its magnitude. The number of input and output ports, expressed as an N x M configuration, characterizes a coupler. The letter N represents the number of input fibers, and M represents the number of output fibers. Fused couplers can be made in any configuration, but they commonly use multiples of two (2 x 2, 4 x 4, 8 x 8, etc.).

Splitter:

Fiber optic splitter is a device that split the fiber optic light into several parts by a certain ratio. The simplest couplers are fiber optic splitters. These devices possess at least three ports but may have more than 32 for more complex devices. Fiber optic splitters are important passive components used in FTTX networks. But two kinds of fiber splitters are popular used, one is the traditional fused type fiber optic splitter (FBT splitter), which features competitive prices; the other is PLC fiber optic splitter, which is compact size and suit for density applications. Both of them have its advantages to suit for different requirement.

Fiber optic splitter typical parameter include input and output part cable length, splitting ratio, working wavelength and with what kind of fiber optic connectors. Just like fiber patch cable, fiber splitters are usually with 0.9mm, 2mm or 3mm cables. 0.9mm outer diameter cable is mostly used in stainless steel tube package fiber optic splitters, while 2mm and 3mm cables are mostly used in box type package fiber splitters. Based on working wavelength difference there are single window and dual window fiber optic splitters. And there are single mode fiber splitter and multimode fiber splitter. Typical connectors installed on the fiber optic splitters are FC or SC type.

Fiber optic couplers or splitters are available in a selection of styles and sizes to separate or combine light with minimal loss. All couplers are produced employing a proprietary procedure that produces reliable, low-cost devices. They’re rugged and impervious to common high operating temperatures. Couplers can be fabricated with custom fiber lengths or with terminations of any type. For more information about Coupler or Splitter, please contact us at sales@fiber-mart.com.fiber-mart.com is your better choice in fiber splitters.

PLC (Planar Lightwave Circuit) Splitter Module Technology

PLC splitter module technology is the latest in passive, fiber-optic component manufacturing. It uses semiconductor (i.e. integrated circuit) fabrication techniques, to build compact, fiber-optic devices. This technique displaces fused-biconical taper devices for high-count splitters. The resulting devices are smaller and more robust.

Planar lightwave circuit (PLC) splitter is a type of optical power management device that is fabricated using silica optical waveguide technology to distribute optical signals from Central Office (CO) to multiple premise locations. It features small size, high reliability, wide operating wavelength range and good channel-to-channel uniformity, and is widely used in PON networks to realize optical signal power splitting. fiber-mart.com provides whole series of 1xN and 2xN splitter products that are tailored for specific applications. All products meet GR-1209-CORE and GR-1221-CORE requirements.

Couplers and Splitter: Couplers are typically used where an aggregate of optical power is required. Therefore, Coupler Module is an assembly, which houses coupler components. These components combine optical power from two or more inputs. And the splitter applications are more common. Typically, they are used for video distribution or for data network monitoring. Inputs are divided and sent to several destinations (e.g. to neighborhoods for CATV). Alternatively, a low-power signal sample is “read-out” with minimal impact, to the link. Therefore, a Splitter Module is an assembly, which house splitter components. These components divide optical power to two or more outputs.

PLC Splitter is based on Planar Lightwave Circuit technology and precision aligning process, can divide a single/dual optical input(s) into multiple optical outputs uniformly and is denoted 1xN or 2xN. PLC splitter is applied in FTTX developments, PON networks, CATV links and optical signal distribution currently. PLC Splitter offers superior optical performance, high stability and high reliability, meets various application requirements in different environments. The high quality performance such as low insertion loss, low PDL, high return loss and excellent uniformity over a wide wavelength range from 1260 nm to 1620 nm, and work in temperature from -40℃ to +85℃.

PLC based on ion exchange in glass has recently been extended to multimode waveguide structures with large core diameter. Monolithic multimode planar waveguides are now commercially available in form of fiber coupled optical waveguide systems. PLC splitter multimode waveguides are well suited for a variety of applications, especially where complex optical functionality needs to be integrated in a monolithic layout. Thus, compact functional elements with low insertion loss and low wavelength dependant losses can be designed for e.g. spectroscopy, medical science, optical power transfer, sensors, data and signal transfer and many others. Through their compact set-up they are easy to combine with lenses, filters and other micro-optical elements.

fiber-mart.com leader in fiber optic plc splitter, providing a range of fiber splitter, such as bare PLC splitter, PLC splitter with fan out, lockless plc splitter module and PLC splitter box and so on, to meet the needs of a variety Applications of engineering design.