Guide to Optical Amplifier

Optical amplifier is an significant device deployed for optical communication and laser physics. No need for converting optical signals into electrical signals first, optical amplifier can directly amplify the optical signals. It is considered to be a laser without optical cavity or with suppressed feedback from cavity. Optical amplifiers are often installed at places where optical signals are weak and need to be enhanced. This ensures the stable transmission of optical signals in the rest cables. Thus, we should attach greater importance to optical amplifier. And this article will guide you to know the secrets of optical amplifier.

optical-amplifier

Functions of Optical Amplifier

In an optical network, optical amplifiers can be used as booster amplifiers, pre-amplifiers or inline amplifiers. These functions are a little different from each other. When a optical amplifier acts as a booster, it is used to amplify the signals that leave the transmitter into the required level before entering into fiber links. The booster amplifier is especially important to a WDM link as the multiplexer attenuates optical signals. Pre-amplifier is used at the other end of a link to amplify the signal level for it to be detected over or above the thermal noise of the receiver. As for inline amplifier, it is used for links over 150 km in case signals become weak in long distance. Every 80 to 100 km, inline amplifier will be placed to make sure that the signal level is over the noise floor.

optical-amplifier-function

Three Types of Optical Amplifiers
1) Erbium Doped Fiber Amplifier (EDFA)

Erbium doped fiber amplifier or EDFA is now the most widely used optical amplifier for long range fiber communications. Its optical fiber (usually a single-mode fiber) at the core is doped with rare earth element erbium to absorb light at one frequency and emit light at another frequency. The light is pumped from laser diodes with a wavelength around 980 nm and sometimes around 1480 nm. EDFA has advantages of high gain, wide bandwidth, high output power, high pumping efficiency, low insertion loss and insensitive to polarization state which turns out to be a good solution for DWDM, CATV and SDH applications.

2) Roman Amplifier

Roman amplifier is designed based on the Roman gain which results from the effect of stimulated Roman scattering. When a lower frequency signal photon induces the inelastic scattering of a higher-frequency pump photon in an optical medium in the nonlinear regime, another signal photon is produced with the surplus energy resonantly passed to the vibrational states of the medium. Roman amplifier is often installed in the mid-stream of a signal or in front of the receiver to amplify signal levels. It has the advantages of greater operating wavelength range, constant optical gain and effective noise figure reduction.

3) Semiconductor Optical Amplifier (SOA)

Semiconductor optical amplifier or SOA is the optical amplifier based on a semiconductor gain medium. Light is sent through a semiconductor single-mode waveguide with transverse dimensions. SOA is usually connected to the output of 1310nm transceivers to amplify signal level before entering into optical fiber. It supports all format of 1310nm wavelength signals and is compatible with all data rates. Thus, SOA is an ideal solution for DWDM network optical amplification.

Conclusion

To sum up, optical amplifier enables the optical transmission over long distance by amplifying signals. This article introduces the fundamentals of its functions and some commonly used types. You may have an overall understanding about optical amplifier. For more information, please visit FS.COM.

The Application of EDFA

1.Introduction
Optical amplifiers is the critical technology for the optical communication networks, enabling the transmission of many terabits of data over distances from a few hundred kilometers to thousands of kilometers by overcoming the fiber loss limitation. As the first optical amplifier commonly used in optical communications systems, EDFA has resulted in a dramatic growth in transmission capacity with the deployment of WDM systems. Be equipped with the features of high output power, high gain, wide bandwidth, polarization independence and low noise figure, EDFAs have become one of the key components used in the new-generation optical communication system. This article is intended to give an overview of EDFA application to help you better understand EDFA.

2.What is EDFA?
Erbium-doped fiber amplifier (EDFA) is an optical repeater device that is utilized to boost the intensity of optical signals being carried through a fiber optic communications system. An optical fiber is doped with the rare earth element erbium so that the glass fiber can absorb light at one frequency and emit light at another frequency.

2.1 Working Principles of EDFA
The erbium-doped fiber (EDF) is at the core of EDFA technology, which is a conventional silica fiber doped with Erbium. When the Erbium is illuminated with light energy at a suitable wavelength (either 980 nm or 1480 nm), it is motivated to a long-lifetime intermediate state, then it decays back to the ground state by emitting light within the 1525-1565 nm band. The Erbium can be either pumped by 980 nm light, in which case it passes through an unstable short lifetime state before rapidly decaying to a quasi-stable state, or by 1480 nm light in which case it is directly excited to the quasi-stable state. Once in the quasi-stable state, it decays to the ground state by emitting light in the 1525-1565 nm band. This decay process can be stimulated by pre-existing light, thus resulting in amplification. The working principles of EDFA are shown in the Figure 1.

working-principle-of-EDFA

Figure 1: The working principles of EDFA

2.2 Baisc configuration of EDFA
EDFA configuration is mainly composed of an EDF, a pump laser, and a component (often referred to as a WDM) for combining the signal and pump wavelength so that they can propagate simultaneously through the EDF. In principle, EDFAs can be designed such that pump energy propagates in the same direction as the signal (forward pumping), the opposite direction to the signal (backward pumping), or both direction together. The pump energy may either be 980 nm pump energy, 1480 nm pump energy, or a combination of both. Practically, the most common EDFA configuration is the forward pumping configuration using 980 nm pump energy, as shown in the Figure 2.

EDFA-configuration

Figure 2: The EDFA configuration with 980 nm pump energy

3.Application of EDFA
As the most advanced technology of optical amplifiers, EDFA is extensively in the optical communication networks. Next we’ll discuss application forms and application fields of EDFA.

3.1 Forms of application

3.1.1 booster amplifier
When used as the booster amplifier, EDFA is deployed in the output of an optical transmitter to improve the output power of the multi-wavelength signal having been multiplexed, as shown in the Figure 3. In this way, distances of optical communication transmission can be extended. This application form places a demand of higher output power on EDFA.

The booster amplifier

Figure 3: The booster amplifier

3.1.2 preamplifier
When used as the preamplifier, EDFA needs the features of low noise and high gain. Being equipped with these features, EDFA can significantly improve the sensitivity of an optical receiver when deployed in the input of an optical receiver, as shown in the Figure 4.

The preamplifier

Figure 4: The preamplifier

3.1.3 line amplifier
When used as the line amplifier, EDFA is able to periodically compensate the transmission loss of lines. As a substitute for OEO repeater, EDFA can directly amplify the optical signals transmitted in lines. In this way, we solve the bottleneck problems of photoelectric interchange to lay a foundation for all-optical network (AON). Figure 5 shows this application of EDFA.

The line amplifier

Figure 5: The line amplifier

3.2 Fields of application
EDFA has the following fields of application:
(1) EDFA can be employed in the high-capacity and high-speed optical communication system. The application of EDFA is very constructive to deal with the problems of low sensitivity of receivers and short transmission distances owing to a lack of OEO repeater.
(2) EDFA can be utilized in long-haul optical communication system. By utilizing EDFA, we can dramatically lower construction cost by increasing the repeater spacing to reduce the quantity of regenerative repeaters. The long-haul optical communication system mainly includes the land trunk optical transmission system and the submarine optical fiber cable transmission system.
(3) EDFA can be used in the optical fiber subscriber access network system. If the transmission distances are too long, EDFA will function as the line amplifier to compensate for the transmission losses of lines, thus greatly increasing the number of subscribers.
(4) EDFA can be employed in wavelength-division multiplexing (WDM) system, especially dense wavelength-division multiplexing (DWDM) system. Utilization of EDFA in WDM system is able to solve the problems of insertion loss and reduce the influences of chromatic dispersion.
(5) EDFA can be utilized in community antenna television (CATV) system. In CATV system, EDFA functions as the booster amplifier to greatly improve the input power of an optical transmitter. Utilizing EDFA to compensate for the insertion loss of optical power splitters can significantly enlarge the scale of the distribution network and increase the number of subscribers.

4.Conclusion
Of the various technologies available for optical amplifiers, EDFA technology is by far the most advanced. Nowadays EDFA is extensively in the optical fiber communication networks. As communication technologies continue to be developed, EDFA will become the preferred choice for the future optical amplifiers. Being equipped with the features of flat gain over a large dynamic gain range, low noise, high saturation output power and stable operation with excellent transient suppression, EDFA will play a more and more important role in optical communication system to better serve subscribers.

Introdution To Optical Amplifiers

1. Introduction:
Optical amplifiers, as the key technology for optical communication networks, have made it possible to transmit many terabits of data over distances from a few hundred kilometers and up to transoceanic distances with wavelength-division multiplexing (WDM) technology, which allows the transmission of multiple channels over the same fiber. The transmission distance of any optical fiber communication system is eventually limited by fiber losses.Optical amplifiers overcome the loss limitation by amplifying the entire WDM signals in strength by several orders of magnitude without requiring conversion of each channel to the electric domain, thus permitting a dramatic increase in capacity of the transmission system and providing the data capacity required for current and future communication networks. The purpose of this passage is to provide an overview of optical amplifiers.

2. The Practical Principles of Optical Amplifiers
A basic optical communication link is composed of a transmitter and receiver, with an optical fiber cable connecting them. Although signals propagating in optical fibers suffer far less attenuation than in other mediums, such as copper, there is still a limit of about 100 km on the distance the signals can travel before becoming too noisy to be detected. Before the advent of optical amplifiers, it was essential to electronically regenerate the optical signals every 80-100 km in order to accomplish transmission over long distances. Although feasible when transmitting a single low-capacity optical channel, it becomes unfeasible when transmitting tens of high-capacity WDM channels, thus resulting in an expensive, powerhungry and bulky regenerator station,

A optical amplifier is designed to directly amplify any input optical signal, without transforming it first to an electronic signal. It can amplify all WDM channels together, and is generally transparent to the number of channels, their bit-rate, protocol, and modulation format. So a single optical amplifier can replace all the multiple components required for an electronic regeneration station. What’s more, the transparency of the optical amplifier means that the link can be upgraded without the need to replace the amplifier.

Optical amplifiers are extensively applied in the optical communication links. Figure 1 shows three ways in which optical amplifiers can be used to enhance the performance of optical communication links. A booster amplifier is used to increase the optical output of an optical transmitter just before a signal enters an optical fiber. The optical signal is attenuated as it travels in the optical fiber. An inline amplifier is used to restore the optical signal to its original power level. An optical pre-amplifier is used at the end of the optical fiber link in order to increase the sensitivity of an optical receiver.

Optical-amplifiers-in-a-optical-communication-link

Figure 1: Optical amplifiers in a optical communication link

3.Types of Optical Amplifiers
There are three most important types of optical amplifiers used in the optical communication network: the erbium-doped fiber amplifier (EDFA), the semiconductor optical amplifier (SOA), and the fiber Raman amplifier (FRA). Each of these amplifiers is introduced as follows.

3.1 Erbium-doped fiber amplifiers
As the first optical amplifier widely used in optical communications systems, EDFA has resulted in a dramatic growth in transmission capacity with the deployment of WDM systems. EDFAs are very widely deployed and become the basis of the vast majority of optically amplified systems. EDFA is an optical repeater device that is used to boost the intensity of optical signals being carried through a fiber optic communications system.

The erbium-doped fiber (EDF) is at the core of EDFA technology, which is a conventional silica fiber doped with erbium. When the erbium is illuminated with light energy at a suitable wavelength (either 980nm or 1480nm), it is motivated to a long-lifetime intermediate state (see Figure 2), then it decays back to the ground state by emitting light within the 1525-1565 nm band. The erbium can be either pumped by 980nm light, in which case it pass through an unstable short lifetime state before rapidly decaying to a quasi-stable state, or by 1480nm light in which case it is directly excited to the quasi-stable state. Once in the quasi-stable state, it decays to the ground state by emitting light in the 1525-1565nm band. This decay process can be stimulated by pre-existing light, thus resulting in amplification.

Pracital-principle-of-EDFA

Figure 2:The practical principle of EDFA

In generally, a EDFA consist of a EDF, a pump laser, and a component (often referred to as a WDM) for combining the signal and pump wavelength so that they can propagate simultaneously through the EDF. In principle EDFAs can be designed such that pump energy propagates in the same direction as the signal (forward pumping), the opposite direction to the signal (backward pumping), or both direction together. The pump energy may either by 980nm pump energy, 1480nm pump energy, or a combination of both. Practically, the most common EDFA configuration is the forward pumping configuration using 980nm pump energy, as shown in Figure 3.

EDFA-configuration

Figure 3: The EDFA configuration

3.2 Semiconductor optical amplifiers
SOAs are amplifiers which use a semiconductor to provide the gain medium. A semiconductor optical amplifier is illustrated in Figure 4. The gain medium is the undoped InGaAsP. This material can be tailored to provide optical amplification at wavelength near 1.3 µm or near 1.5 µm, which is the significant wavelength for optical communications. Other semiconductors can be used to amplify optical signals at other wavelengths. The input and output faces of the amplifier are antireflection-coated in order to prevent optical feedback to the gain medium and lasing.

A-semiconductor-optical-amplifier

Figure 4: A semiconductor optical amplifier

SOAs operate in a similar way to standard semiconductor lasers (without optical feedback which causes lasing), and are packaged in small semiconductor “butterfly” packages. Unlike other optical amplifiers, they are pumped electronically and a separate pump laser is not required. SOAs are less expensive and therefore suitable for using in local networks where best performance is not required but cost is an important factor.Despite their small size and potentially low cost due to mass production, SOAs suffer from a number of drawbacks which make them unsuitable for most applications. In particular, they provide relatively low gain, have a low saturated output power and relatively high noise factor (NF). These drawbacks makes SOAs unsuitable for multichannel application but fit for some single channel which don’t require high gain and high output power.

3.3 Fiber Raman amplifiers
A fiber Raman amplifier is shown in Figure 5. The gain medium is undoped fiber. Power is transferred to the optical signal by a nonlinear optical process known as the Raman effect. Power to supply the optical gain is offered by an optical pump. The wavelengths that experience optical gain are decided by the wavelength of the optical pump, so the Raman amplifier can be tailored to amplify a given optical wavelength by proper selection of the pump wavelength. The optical gain in a Raman amplifier is distributed over a long span of optical fiber. Typically, the optical pump is introduced at the end of a length of fiber in order to provide optical gain that increases towards the end of the fiber.

A-fiber-Raman-amplifier

Figure 5: A fiber Raman amplifier

In a Raman amplifier, the signal is amplified due to stimulated Raman scattering (SRS). Raman scattering is a process in which light is scattered by molecules from a lower wavelength to a higher wavelength. SRS is a nonlinear interaction between the signal and the pump and can take place within any optical fiber. In most fibers however the efficiency of the SRS process is low, high pump power (typically over 1 W) is required to obtain useful signal gain. Thus, in most cases Raman amplifiers cannot compete effectively with EDFAs. On the other hand, Raman amplification provides two unique advantages over other amplification technologies. The first advantage is that the amplification wavelength band of the Raman amplifier can be tailored by changing the pump wavelengths, and thus amplification can be achieved at wavelengths without being supported by competing technologies. The second, more important, advantage is that amplification can be achieved within the transmission fiber itself, enabling what is known as distributed Raman amplification (DRA). In this process high pump power is launched into the transmission fiber in order to provide amplification for the signal as it travels along the fiber. Since gain occurs along the transmission fiber, DRA prevents the signal from being attenuated to very low powers. Raman amplifiers are often used together with EDFAs to offer ultra-low NF combined amplifiers, which are useful in applications such as long links without inline amplifiers, ultra-long links expanding thousands of kilometers, or very high bit-rate links.

4.Conclusion
Optical amplifiers are  the critical technology for the optical communication networks, enabling the transmission of many terabits of data over distances from a few hundred kilometers and up to thousands of kilometers by overcoming the fiber loss limitation. Through concretely introducing optical amplifiers above, I hope this passage can help you get better understanding of optical amplifiers.

Fiber Optics Products used in the Fiber Optical Transmission

Many fiber optic applications amplification from the optical transmission. For example, long-haul DWDM techniques, Previously, it uses expensive electronic of the optical signal every 100 kilometres. The current contemporary long-haul DWDM techniques make use of a number of sophisticated optical elements to change several repeaters having a solitary optical gadget. These types of optical products are used widely in the fiber optic network.

Fiber Optic Video Transmission

The fiber used in a EDFA which actually doped along with erbium, the uncommon planet component which has the right energy within it’s atomic framework in order to enhance gentle from 1550 nm. The 980 nm or even 1480 nm “pump” laser beam injects power to the erbium-doped fiber. Whenever a fragile transmission from 1550 nm makes its way into the actual fiber, the actual encourages the actual erbium atoms release a their own saved power because extra 1550 nm gentle. This method proceeds since the transmission goes by lower the actual fiber, developing more powerful as well as more powerful till this gets to the actual erbium-doped area.

The figure showed the two-stage EDFA mid-stage entry, an essential component of high overall performance fiber optic techniques. In this instance, 2 easy single-stage EDFAs tend to be packed collectively. The consumer gets the actual result from the very first phase EDFA and also the enter from the 2nd phase EDFA. These types of techniques frequently need the actual regular utilization of extra components. Putting the actual DCF in the mid-stage entry stage from the two-stage EDFA decreases dangerous results about the program. The consumer nevertheless understands substantial obtain with the EDFA, actually with the help of the actual higher optical reduction bit of DCE.

two stage

EDFAs prevent the majority of energetic elements simply because photons enhance the actual transmission. The actual EDFA supplies a higher result energy, needing less amplifiers inside a provided program style. The standard EDFA style amplifiers gentle on the pretty thin, just 12 nm. The actual add-on associated with obtain equalization filter systems may boost the music group in order to a lot more than twenty five nm. Additional unique doped materials boost the amplification group in order to forty nm or even more. In addition, information price self-reliance within EDFAs indicates something update demands altering just the actual release as well as obtain terminals.

The actual EDFA’s dependable overall performance causes it to be helpful within long-haul, higher information price fiber optic marketing communications techniques as well as CATV shipping techniques. Within CATV programs, EDFA’s increase the transmission prior to as well as following a good optical splitter in order to enhance the actual divided transmission with regard to more than a number of materials. Generally, 4 main programs can be found with regard to optical amplifiers: energy amplifier/booster, in-line amplifiers, preamplifier or even reduction payment with regard to optical systems.

EDFA Amplifier

Scientists created erbium-doped fiber amplifiers (EDFAs) to change several numerous electronic repeaters along with less optical repeaters, general decreasing program price as well as intricacy EDFAs, like the figure, permit easy techniques updates with the addition of extra resources in order to various wavelengths as well as mixing all of them on to just one fiber utilizing a DWDM multiplexer.

edfa

In-line Amplifier

The actual in-line amplifier or even inline repeater requires a little enter transmission as well as increases this with regard to retransmission lower the actual fiber. Managing the actual samll transmission overall performance as well as sound will give you much better program outcomes. Sound additional through amplifiers within sequence may restrict the machine duration.

Booster amplifier

Enhancer amplifier they fit straight following the optical transmitter. The actual EDFA should produce the most feasible result degree i’m regards to the actual big transmission enter. Little transmission reaction isn’t because essential since the immediate transmitter result is generally 10 dBm or more. The bigger SNR from the inbound indicators offers much less effect compared to results from the sound additional through the amplifier.

Have a Special Look at Fiber Optic Amplifier

Wiki of Fiber Optic Amplifier

An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed. Optical amplifiers are important in optical communication and laser physics.

Standard of Fiber Optic Amplifier

We know Fiber Optical Amplifiers that design from simple single stage to more complex multistage amplifiers with variable gain evolved as a different viator for system performance by equipment manufacturers and were initially made in house. More recently, the equipment vendors outsourced the design and manufacturing of amplifiers to the component vendors while requiring more than one source in order to control cost and delivery risk. This led to a pseudo-standardization of optical amplifiers with three or four vendors making amplifiers with compatible optical, mechanical,electrical hardware, and software specification.

Optical amplifier is dominated by erbium-doped fiber amplifiers and the leading suppliers have been shipping amplifiers for 10 years or longer. These companies include Oclaro, JDS Uniphase, and Furukawa. Ovum estimates these companies enjoy more than 60% market share of the nearly 200 dollars merchant erbium-doped fiber amplifier market in 2008. Well Fiberstore’s In-line Amplifier is on hot sale.

There are another 25 companies fighting for the remaining revenues. Twenty-one of the remaining optical amplifier companies that still exist today started between 1997 and 2003. All the amplifier suppliers in low cost regions started between 1998 and 2003. And only two new amplifier suppliers have entered the market since 2003, Manlight and Titan Photonics. The Figure showed the optical amplifier for next WDM networks

optical amplifier

Optical Amplifier: Present Status

After nearly five years of focus on cost reduction and reduces progress in innovation. New direction in optical amplifier technology are becoming visible. These are in response to the major trends for the amplified optical networks of higher degree of connectivity and introduction of channels at higher data rates. Agility in amplifiers will be key to the successful deployment of ROADM networks requiring seamless provisioning and recovery in the event of failures. Features such as fast gain control at sub millisecond timescale and rapid spectral adjustments to counter the impairments due to higher order effects (spectral hole during[SHB], Raman spectral tilt in fiber, and polarization dependent loss [PDL]) of components) will be needed on an integrated basis across the whole system. Likewise, continuous demand to increase the OSNR of the signals to support ever increasing channel rates to 100 Gb/s and beyond over ultra-long-haul distances will require every dB to be made available, for example by deployment of hybrid Raman/EDFAs at every repeater site in the network. Another trend is the deployment of high-power cladding pumped amplifiers with watts of output power in the access network for distribution of video and other content. From the commercial standpoint, however, since the industry has become addicted to 15% to 20% price reduction year to year, these new features will have to be delivered at negligible incremental cost.

Warm tips: Fiberstore is a professional fiber optics products supplier, includes different fiber optical amplifier, such as Booster Amplifier, CATV fiber amplifier, DWDM amplifier and EDFA amplifier, even Fibre Splitter, if there you need, welcome to visit our main website: www.fiberstore.com