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.

Introduction of the Transients in Optical WDM Networks

by http://www.fiber-mart.com

A systems analysis continues to be completed to consider dynamical transient effects in the physical layer of an Optical WDM Network. The physical layer dynamics include effects on different time scales. Dynamics from the transmission signal impulses possess a scale of picoseconds. The timing recovery loops in the receivers be employed in the nanoseconds time scale. Optical packet switching in the future networks will have microsecond time scale. Growth and development of such optical networks is yet continuing. Most of the advanced development work in optical WDM networks is presently focused on circuit switching networks, where lightpath change events (for example wavelength add/drop or cross-connect configuration changes) happen on the time scale of seconds.
It is focused on the dynamics from the average transmission power associated with the gain dynamics in Optical Line Amplifiers (OLA). These dynamics may be triggered by the circuit switching events and have millisecond time scale primarily defined by the Amplified Spontaneous Emission (ASE) kinetics in Erbium-Doped Fiber Amplifiers (EDFAs). The transmission power dynamics will also be influenced by other active components of optical network, for example automatically tunable Optical Attenuators, spectral power equalizers, or other light processing components. When it comes to these dynamics, a typical power of the lightpath transmission signal is recognized as. High bandwidth modulation from the signal, which actually consists of separate information carrying pulses, is mostly ignored.
Ring WDM networks implementing communication between two fixed points are very well established technology, in particular, for carrying SONET over the WDM. Such simple networks with fixed WDM lighpaths happen to be analyzed in many detail. Fairly detailed first principle models for transmission power dynamics exist for such networks. These models are implemented in industrial software allowing engineering design calculations and dynamical simulation of these networks. Such models could possibly have very high fidelity, but their setup, tuning (model parameter identification) and exhaustive simulations covering a variety of transmission regimes are potentially very labor intensive. Adding description of new network components to such model could need a major effort.
The problems with detailed first principle models is going to be greatly exacerbated for future Mesh WDM networks. The near future core optical networks will be transparent to wavelength signals on a physical layer. In such network, each wavelength signal travels through the optical core between electronic IP routers around the optical network edge using the information contents unchanged. The signal power is attenuated in the passive network elements and boosted by the optical amplifiers. The lightpaths is going to be dynamically provisioned by Optical Cross-Connects (OXCs), routers, or switches independently on the underlying protocol for data transmission. Such network is basically a circuit switched network. It might experience complex transient processes of the average transmission power for every wavelength signal at the event of the lightpath add, drop, or re-routing. A mix of the signal propagation delay and channel cross-coupling might result in the transmission power disturbances propagating across the network in closed loops and causing stamina oscillations. Such oscillations were observed experimentally. Additionally, the transmission power and amplifier gain transients could be excited by changes in the average signal power because of the network traffic burstliness. If for some period of time the wavelength channel bandwidth is not fully utilized, this could result in a loss of the average power (average temporal density of the transmitted information pulses).
First circuit switched optical networks are already being designed and deployed. Fraxel treatments develops rapidly for metro area and long term networks. Engineering design of circuit switched networks is complicated because performance has to be guaranteed for all possible combinations of the lightpaths. Further, as such networks develop and grow, they potentially need to combine heterogenous equipment from a variety of vendors. A system integrator (e.g., fiber-mart) of such network might be different from subsystems or component manufacturer. This creates a necessity of developing adequate means of transmission power dynamics calculations which are suitable for the circuit switched network business. Ideally, these methods should be modular, independent on the network complexity, and use specifications on the component/subsystem level.
fiber-mart has technical approach to systems analysis that’s to linearize the nonlinear system around a fixed regime, describe the nonlinearity like a model uncertainty, and apply robust analysis that guarantees stability and gratifaction conditions within the presence of the uncertainty. For a user of the approach, there is no need to understand the derivation and system analysis technicalities. The obtained results are very simple and relate performance to basic specifications of the network components. These specifications are somewhat not the same as those widely used in the industry, but could be defined from simple experimentation using the components and subsystems. The obtained specification requirements may be used in growth and development of optical amplifiers, equalizers, optical attenuators, other transmission signal conditioning devices, OADMs, OXCs, and any other optical network devices and subsystems influencing the transmission power.

Optical Amplifier Used in CATV Transmission Network

by http://www.fiber-mart.com

CATV technology has matured steadily over the past several years, and has expanded into diverse applications. However, as the quick expansion in technology and services, it’s important to improve CATV network component performance for higher visual and audio signals transmission. Optical amplifier for CATV application is the key element in such transmission. This post intends to give a clear introduction of optical CATV amplifier and its application in CATV transmission.
Introduction to CATV Amplifier
CATV amplifier is also a type of EDFA (Erbium Doped Fiber Amplifier) amplifier which is the most popular optical amplifier in optical network communications. It is mainly used to amplify damped TV signals (compensation for loss) for improved signal quality before sending them to each subscriber. Moreover, CATV amplifiers not only amplify the signal, but also amplify the noise on the line, and bring some return loss. That’s why a quality CATV amplifier price is a little high, because it can provide better performance for the whole network transmission.
Why CATV Amplifier Is Needed?
As we all know, CATV network is a multi-channel TV system to transmit high quality video and sound signal from a large number of digital or analog broadcast television and radio channel via fiber optic cable or coaxial cable. CATV amplifier often acts as booster optical amplifier in this system to get satisfying transmission effect. The following picture illustrates a basic long haul CATV transmission system using EDFA amplifier.
In most cases, the satellite providers deliver high quality digital video and audio to users’ home depending on the users’ equipment. However, the signal incoming cable feed is connected to more than one equipment with use of optical splitters. And if the incoming signal gets fragmented and rerouted, the overall speed and quality will be worse. Under this condition, an optical amplifier can be used to boost the signal power and help users get better services.
CATV Amplifier in Long-Haul CATV Transmission System
As have mentioned above, a basic long-haul CATV communication link consists of head end, transmitter, receiver, optical amplifier, and sometimes fiber splitter is also needed in this type of transmission network. The head end receives TV signals off the air or from satellite feeds, and supplies them to the transmission system. The optical splitters are often utilized in a poin-to-multipoint configuration. Here are two CATV fiber network cases using CATV booster amplifier.
Case one
This is a point-to-multipoint medium size private CATV network. In the head end, the transmitter receives signals from the RF combiner on the 1310nm or 1550nm wavelength. Then the signals split into several parts and are received by the CATV receiver. Finally, all the signals are amplified by the CATV amplifier and sent to the subscriber.
Case two
In the above application case, the optical amplifier lies behind the CATV receiver, but in this case, it’s a little different.
As we can see from the graph, the CATV amplifier lies in the front of the receiver to boost the transmission distance longer. Except for that, this transmission network also deploys two DWDM Mux/Demux to multiply the eight different wavelengths into one fiber for better transmitting. Please note that this graph just illustrates part of the long-haul CATV system.

 

Wavelength Division Multiplexing (WDM) Increases Network Capacity

WDM is a method of separating or combining multiple wavelengths out of or into a single fiber strand with each wavelength carrying a different signal. Using optical filters lets a certain range of wavelengths pass through, while another range is allowed. Thin-film filter technology (TFF) is often used to achieve this effect. Multiple thin layers are stacked and interference effects are created by sequential reflections on the interface between the layers. This lets light reflect for certain wavelengths and pass through for others.
The capacity of a network can be increased cost effectively by using WDM. Two types of WDM are commonly used:
Dense Wave Division Multiplexing (DWDM) devices are mainly used when more wavelengths are required between sites and when the network extends over a very long distance. Forty wavelength channels from 1530 nm to 1570 nm are distributed in the C-band. To increase capacity, DWDM can be overlaid on a CWDM infrastructure.
Coarse Wave Division Multiplexing (CWDM) has 18 different wavelength channels standard, spaced 20 nanometers (nm) apart between 1270 nm and 1610 nm. Most systems only use the top eight channels between from 1470 nm and 1610 nm. CWDM systems have the advantage that they can always be upgraded at a later stage. This limits the initial installation costs. The requirements on the lasers is not severe due to the wide channel spacing, allowing less expensive lasers without any temperature control to be used.
The insertion loss of DWDM and CWDM is typically lower than that of optical splitters. This increases the reach of a network from a centralized office substantially. As every customer has wavelength(s) assigned to them, this provides better security and makes eavesdropping virtually impossible.
WDMs Can Be Utilized In Different Ways:
Add/Drop Vs Mux/Demux.
A multiplexer, also known as a mux, combines several wavelength channels on one fiber, while a de-multiplexer (demux) separates them at the other side. A mux/demux configuration is very useful to increase a fiber’s end-to-end capacity. A mux is normally located at a central office, while demuxes are placed in either a splice closure or cabinet. From there the fibers are routed in a star-shaped topology to their ultimate destination.
An alternative to separating the wavelengths at one side, individual wavelengths can be added or dropped at various points across the line. This process does not affect other wavelengths. This is often preferable when the distance between sites is long or they are grouped in a circular structure.
One Or Two Fibers?
An alternative to sending signals at different wavelengths through the same fiber is to use two different fibers. Many CWDM systems use two fibers where one is used for upstream signals and the other for downstream. In this configuration, each customer uses two fibers and one wavelength. Each customer will have two wavelengths if they use a single fiber.

Utilizing the WDM – Increase Fiber Capacity Without Construction

Imagine turning a dirt road into a multilane highway without having to perform any new construction. That is what Wave Division Multiplexing (WDM) allows with an existing fiber network. This technology can greatly reduce the cost of increasing network capacity without having to move a single shovelful of dirt or hang a single new fiber.
WHY WDM?
It’s no secret that outside-plant (OSP) fiber construction is expensive. Construction costs vary, but they are always hefty, and they increase greatly if cable is buried. In addition to construction, the costs of permitting, zoning, raw materials and splicing are significant. Thus, avoiding installing new fiber is best whenever possible.
Many communications providers are experiencing fiber exhaust in their networks. This means that the cable counts initially deployed are not able to handle today’s needs. Now, emerging technologies in cell backhaul, business class services and others are creating a need for yet more fibers. However, in most cases, ever-increasing labor and material prices make new fiber construction too costly to consider for many projects.
WDM allows operators to place new equipment at either end of a fiber strand and combine multiple wavelength channels on a single fiber strand. Many existing systems use only a small amount of the spectrum available on single piece of glass. Using either coarse wave-division multiplexing (CWDM) or dense wave-division multiplexing (DWDM), operators can combine many different services on a single fiber by assigning a different color, or wavelength, to each service. Multiplexers are used to combine all these wavelengths onto a single fiber, and demultiplexers are used to separate the colors farther on in the network.
Mobile devices, cloud computing, over-the-top video, DOCSIS 3.1 with IPTV, and online gaming are just a few of the drivers for increased bandwidth demand. As demand continues to rise, service providers will need long-term strategies to develop a bigger pipe.
Cellular backhaul, FTTx and commercial business services are also creating a need for more fiber capacity. 3G and 4G cellular services require more bandwidth than cellular services needed in years past and therefore require a fiber link to each cell site. A provider may own a fiber sheath that runs right past a cell tower, but all its fibers may currently be used to maximum capacity. Providing lit services or dark fiber to cell towers can be very profitable but not if it requires plowing or hanging new fiber to these cell sites.
Business-class services are becoming popular revenue sources for communications companies. Businesses are often willing to sign long-term contracts and pay more than residential customers. In some cases, businesses require fiber to meet their bandwidth needs. The same issue arises here: How is it possible to serve these new customers without having to install new OSP fiber to those sites?
WDM TO THE RESCUE
Most legacy fiber networks use a single wavelength, or color, on each fiber. Think of it as two people on different mountaintops using white-lens flashlights to communicate via Morse code – not very sophisticated, but it works.
All of a sudden, two more people want to start communicating between those two mountaintops. What is the solution? Use different colored lenses on the flashlights to communicate. Senders and receivers will recognize and send only their own colors of light and ignore the others.
This is basically what a WDM network does. It uses multiple colors of light over the same medium (fiber). Transmitters tuned to specific wavelengths send light into a passive combiner called a mux (short for multiplexer). All the wavelengths travel down the common fiber and are separated using a passive demultiplexer (also called a demux). Now each receiver at the other end will be able to receive just its own discrete signal.
In other words, WDM maps multiple optical signals to individual wavelengths and multiplexes the wavelengths over a single fiber. WDM can carry multiple protocols without having to convert them to a common signal format. A single fiber is able to do virtually anything that’s needed.
There are two main types of WDMs. The advantage of CWDM technology is that it is relatively inexpensive compared with DWDM. The transmitters used in CWDM are less expensive, as they do not need to be tuned as precisely as DWDM transmitters. However, CWDM has drawbacks, too: Only 18 channels are available, and fiber amplifiers cannot be used with them. Thus, they are not the ideal choice for long-haul networks.
CWDM channels each consume 20 nm of space and together use up most of the single-mode operating range. The wavelengths most commonly used are the eight channels in the 1470 to 1610 nm range. Any transceiver used in CWDM applications operates within one of these channels.
DWDM allows many more wavelengths to be combined onto one fiber. It also leverages the capabilities of fiber amplifiers, which can amplify the 1550 nm or C band commonly used in DWDM applications. This makes it ideal for use in long haul and areas of greater customer density. Instead of the 20 nm spacing in CWDM (equivalent to about 15 million GHz), DWDM uses either 50, 100 or 200 GHz spacing in the C and sometimes the L bands. This allows many more wavelengths to be packed onto the same fiber.
The downside of DWDM is that the lasers need to be much more accurate and require precise temperature ranges to operate. This makes DWDM applications much more expensive than CWDMs. The introduction of the ITU-T G.694.1 grid in 2002 made integrating DWDM technology easier. It created an industry standard for DWDM.
CHOOSING A TYPE OF WDM
Before deploying any WDM equipment, it is necessary to ensure that the glass in place will support all the required wavelengths. Low-water-peak or zero-water-peak fiber is more suitable for WDM applications, and older glass types may have water peak issues. If the glass is too old, it may be necessary to bite the bullet and install some new fiber.
Assuming the glass is appropriate for WDM, should you use CWDM or DWDM technology to solve fiber exhaust problems? As previously noted, CWDM can support a maximum of 18 channels and is not ideal for long haul. So CWDM would typically be best for applications that do not require the signal to travel great distances and in locations where not many channels are required. The availability of SFP transceivers may also be a limiting factor.
For applications that require a high number of channels or for long-haul applications, DWDM is the ideal solution. Though the electronics and passives are not cheap, they are considerably more cost-effective than putting in new fiber.
DESIGN CONSIDERATIONS
It’s important to ensure that the CWDM and DWDM passives will operate properly in the environment where they will be placed. This becomes especially important when putting CWDM passives in the outside plant. Before buying a mux or demux for use in an unconditioned cabinet or splice case, verify that the operating temperature will fit the application. Many vendors specify the storage temperature but not the operating temperature.
The operating temperature of an optical component is the actual temperature range in which the component will work. Usually, a component must remain within a specified temperature range to perform at a specified optical performance level.
The storage temperature of an optical component is the temperature at which an optical component can be stored without causing any degradation or component failure when it is used in the component’s specified operating temperature limits. Some storage temperatures can exceed the actual operating temperature of the components. When sourcing WDM filters, ensure that they will be able to operate within the temperatures in which they will be deployed.
Another design consideration with any WDM network is insertion loss. Though WDM creates a huge increase in capacity, it also creates insertion loss in a network. Using the maximum insertion loss values in the link budget is a good idea; keep in mind that some manufacturers do not include the connector loss if the device is terminated.
Calculate the loss for both the mux and demux components. The maximum insertion loss on a typical eight-channel CWDM is 3 dB, so for a mux/demux solution, add 6 dB of insertion loss.
WDM filters can be designed to drop individual colors at a specific location and keep sending the rest down the fiber path. In some applications, combining several wavelengths at a certain location and then dropping individual channels to customers along the same route may be desirable. This is the most common type of design used in fiber-to-the business and cell tower applications.
SUMMARY
WDM technology is a very effective method for overcoming fiber exhaust. Placing passive filters and WDM transceivers at each end of a fiber optic network can greatly increase bandwidth without having to spend capital on new fiber construction projects. Most current fiber technologies use only a small sliver of the available bandwidth capacity of single-mode glass, so a properly designed WDM network can unlock a floodgate of available power in a network. Using many channels on the same piece of optical fiber enables operators to serve businesses, cell towers and residential customers with the same fiber. Fiber counts are no longer a constraint.