Evolution of Optical Wavelength Bands

As fiber optic networks have developed for higher speeds, longer distances, and wavelength-division multiplexing (WDM), fibers have been used in new wavelength ranges, namely "bands". Fiber transmission bands have been defined and standardized, from the original O-band to the U/XL-bands. This article will mainly illustrate the evolution of the typical fiber transmission bands used for different optical telecom systems.

Among these bands, the O-band, also called the Original-band, was the first band used in optical telecommunication because of the small pulse broadening (small dispersion); Single-mode fiber transmission began in the "O-band" just above the cutoff wavelength of the SM fiber developed to take advantage of the lower loss of the glass fiber at longer wavelengths and availability of 1310nm diode lasers.

The E-band represents the water peak region while the U/XL-band resides at the very end of the transmission window for silica glass. The E-band (water-peak band) has not yet proven useful except for CWDM. It is probably mostly used as an extension of the O-band but few applications have been proposed and it is very energy-intensive for manufacture. The E-band and U/XL-bands usually are avoided because they correspond to high transmission loss regions.

To take advantage of the lower loss at wavelength of 1550nm, fiber was then developed for the C-band. The C-band is commonly used along with the development of ultra-long distance transmission with EDFA and WDM technologies. As transmission distances became longer and fiber amplifiers began being used instead of optical-to-electronic-to-optical repeaters, the C-band became more important. With the advent of DWDM (dense wavelength-division multiplexing) which enables multiple signals to share a single fiber, the use of C-band was expanded.

With the development of fiber amplifiers (Raman and thullium-doped), DWDM system was expanded upward to the L-band, leveraging the wavelengths with the lowest attenuation rates in glass fiber as well as the possibility of optical amplification. Erbium-doped fiber amplifiers (EDFAs, which work at these wavelengths) are a key enabling technology for these systems. Because WDM systems use multiple wavelengths simultaneously, which may lead to much attenuation. Therefore optical amplification technology is introduced.

Despite great expectations, the number of installed systems using all-Raman solutions worldwide can be counted on one hand. In the future, however, the L-band will also prove to be useful. Because EDFAs are less efficient in the L-band, the use of Raman amplification technology will be re-addressed, with related pumping wavelengths close to 1485nm.

Although CWDM is now considered as a low-cost version of WDM that has been in use, most do not work over long distances. The most popular is FTTH PON system, sending signals downstream to users at 1490nm (in S-band) and using low cost 1310nm transmission upstream. Early PON systems also use 1550 downstream for TV, but that is being replaced by IPTV on the downstream digital signal at 1490nm. Other systems use a combination of S, C and L bands to carry signals because of the lower attenuation of fibers. Some systems even use lasers at 20nm spacing over the complete range of 1260nm to 1660nm but only with low water peak fibers.

Although various wavelength bands of the O-, S-, C- and L- bands have come into use with the explosive expansion of the traffic in recent years, the optical fiber amplifiers for the O- and S-band wavelengths were not realized for many years because of many technical hurdles. C- and L-band most commonly used in fiber optic networks will play more and more important roles in optical transmission system with the growth of FTTH applications.

Originally published at http://www.china-cable-suppliers.com

Identify Various Ports on WDM Mux/Demux

In today’s world of intensive communication needs and requirements, fiber optic cabling has become increasingly popular. But considering the physical fiber optic cabling is expensive to implement for each individual service, using a Wavelength Division Multiplexing (WDM) for expanding the capacity of the fiber to carry multiple client interfaces is highly advisable. WDM MUX/DEMUX (Multiplexer/De-Multiplexer) is one of the most important components in WDM systems. But there are so many types of ports which are not so easy to identify. This article will illustrate various ports with different functions on WDM Mux/Demux.

Common Ports on WDM Mux/Demux

For WDM Mux/Demux, channel port and line port are the most common and necessary ports for normal operation of the WDM Mux/Demux.

Channel Port

CWDM uses 18 wavelengths ranging from 1270nm to 1610nm with channel intervals of 20nm. Channel ports on CWDM MUX/DEMUX is usually ranging from 2 to 18. DWDM uses the wavelength ranging from 1470nm to 1625nm usually with the channel port ranging from 4 to 96. Since DWDM Mux/Demux has a more dense channel spacing of 0.8 nm (100 GHz) or 0.4 nm (50 GHz), it is more suitable for high-density networks.

Line Port

There are two types of line port available for CWDM and DWDM MUX/DEMUX. One is dual fiber line port, and the other is single fiber line port. The wavelengths order and the applications of them are totally different. Dual-fiber line port is used for bidirectional transmission, which means the TX port and RX port of every duplex channel port supporting the same wavelength. The WDM MUX/DEMUXs with dual fiber line ports installed on the two ends of the network could be the same. Single-fiber line port only support one direction data flow. If you choose a single-fiber WDM MUX/DEMUX on one side of the network, there should be a single-fiber WDM MUX/DEMUX which supports the same wavelengths but has the reverse order on the TX port and RX port of every duplex channel port.

Special Ports on WDM Mux/Demux

1310nm Port and 1550nm Port

1310nm and 1550nm ports are wavelength ports of WDM MUX/DEMUX. Since a lot of optical transceivers use these two wavelengths for long-haul network, adding these two ports when the device does not include these wavelengths is very important. CWDM Mux/Demux can add either type of wavelength ports, but the wavelengths which are 0 to 40 nm higher or lower than 1310 nm or 1550 nm cannot be added to the device. However, DWDM Mux/Demux can only add 1310nm port.

Expansion Port

Expansion port which can be added on both CWDM and DWDM Mux/Demux is a special port to increase the number of available channels carried in the network. It means that when a WDM Mux/Demux can not meet all the wavelength needs, it is necessary to use the expansion port to add different wavelengths by connecting to another WDM Mux/Demux’s line port.

Monitor Port

This port is used to monitor or test the power signal coming out of a Muxed CWDM or before it gets demuxed from the signal coming through the fiber network usually at a 5% or less power level. Generally, it can be connected with measurement or monitoring equipment, such as power meters or network analyzers.

No matter the common ports or the special ports on WDM Mux/Demux have their own features and application. FS.COM WDM products designed for easy and fast implementation take up minimal space and use least power, thus providing the highest integration level of CWDM and DWDM networks. They can also provide complete solutions for CWDM and DWDM. Kindly contact sales@fs.com for more details if you are interested.

Installation Guide for RJ45 Modular Jack on CAT5e Shielded Cable

RJ45 modular jack is used for mounting optical connectors into the wall plate or patch panel for network wiring installs. There are numerous requests for wiring diagrams or general information on how to punch down or terminate keystone jacks (Cat5e / Cat6) after running your telecom network's cross-connect cabling. Building a patch cable involves installing RJ45 plug connectors on each end of a stranded cable. Here we describe the process of installing the RJ45 connectors.

Attaching cable connectors involves the use of very sharp knives for stripping cable insulation as well as crimping tools that can be dangerous to operate. Many crimping tools incorporate a ratchet mechanism that, once engaged, prevents the tool from being opened until it has first closed completely. Anything caught in the crimping tool, including your fingers, will be crushed.

Step1

Cut cable to needed length. Remove the outer jacket of the cable using the Cable Prep Tool. Place the tool approximately 1.5” from end of the cable. Rotate tool at least twice around the cable, both clockwise and counter-clockwise. That will score the jacket allowing you to remove it without damaging the conductors inside the jacket.

Carefully strip away a few inches of the outer insulation from the twisted-pair cable, revealing the individually insulated twisted-pair conductors inside. Each twisted-pair conductor consists of a set of thin stranded wire surrounded by insulation. Do not cut the insulation of the twisted-pair conductors.

Step2

Orient the conductors according to the colors of the insulation. Pull the wire braid back over the outer jacket. Trim off the clear plastic jacket.

Step3

Straighten out the twisted-pair conductors, arrange them and cut the conductors to a length about 12mm. Leave the insulation in place on the individual twisted-pair conductors. Make sure that the conductors are all cut to the same length, providing a square end to the cut. Untwist and separate all of the conductor pairs.

TIP: Use the jacket that was just removed and feed each conductor down the jacket to untwist it. Bonded twisted pair cable can be separated using a 1797B cable separator.

Step4

Use the outer edge of the cable scissors to straighten conductors. Using gentle pressure (to avoid damage to the conductors), put each conductor between thumb and edge of cutter and pull up from outer jacket to end of the conductor.

Step5

Arrange the conductors in the order shown: 1. White/Orange 2. Orange 3. White/Green 4. Blue 5. White/Blue 6. Green 7. White/Brown 8. Brown

Step6

Bring the sorted conductors together, holding tightly between the thumb and forefinger. Recheck to ensure the wiring sequence is correct. Cut the wires at a 90º angle about 1/2” from the end of the jacket.

Step7

Insert the conductors into the plug. Hold the plug with the copper contacts facing up and the locking tab facing down. In this position, the orange/white conductor should be the first conductor on the left. Insert the conductors into the plug. Make sure the drain wire is wrapped around the jacket underneath the back of the plug prior to crimping in order to complete the ground.

Step8

Crimping the plug using the cable crimping tool. Place the plug into the crimp tool and squeeze handles tightly. The copper splicing tabs on the plug will pierce into each of the eight conductors. The locking tab will cinch onto the outer jacket of the cable.

Step9

Remove plug from tool. Check the conductor sequence and ensure outer jacket is inside the plug and secured by the locking tab. Trim excess drain wire just below entry into plug.

Step10

Repeat steps for other end of cable. Then use a cable tester to ensure proper installation and wiring of plugs.

Why Is Fiber Optic Technology 'Faster' than Copper?

The deployment of fiber optics in telecommunications and wide area networking has been common for many years, but more recently fiber optics have become increasingly prevalent in industrial data communications systems as well. Fiber optic technology uses pulses of light to carry data along strands of glass or plastic. It's the technology of choice for the government's National Broadband Network (NBN) and data centers, which promises to deliver next-generation 200G and 400G Ethernet speeds.

When talking about 'speed', we were actually talking about throughput (or capacity) — the amount of data you can transfer per unit time, says Associate Professor Robert Malaney from the University of New South Wales, School of Electrical Engineering and Telecommunications.

And fiber optics can definitely transfer more data at higher throughput over longer distances than copper wire. For example, a local area network using modern copper lines can carry 3000 telephone calls all at once, while a similar system using fiber optics can carry over 31,000.

So what gives it the technical edge over copper wires? Traditional copper wires transmit electrical currents, while fiber optic technology sends pulses of light generated by a light emitting diode or laser along optical fibers.

In both cases you're detecting changes in energy, and that's how you encode data. With copper wires you're looking at changes in the electromagnetic field, the intensity of that field and perhaps the phase of the wave being sent down a wire. With fiber optics, a transmitter converts electronic information into pulses of light — a pulse equates to a one, while no pulse is zero. When the signal reaches the other end, an optical receiver converts the light signal back into electronic information.

The throughput of the data is determined by the frequency range that a cable will carry — the higher the frequency range, the greater the bandwidth and the more data that can be put through per unit time. And this is the key difference — fiber optic cables have much higher bandwidths than copper cables (eg. cat5e copper cable).

"Optical fiber can carry much higher frequency ranges — note that light is a very high frequency signal — while copper wire attenuates or loses signal strength at higher frequencies," says Malaney.

Also, fiber optic technology is far less susceptible to noise and electromagnetic interference than electricity along a copper wire.

"You can send the signal for over 200 km without any real loss of quality while a copper cable signal suffers a lot of degradation over that distance," says Malaney.

As well as a significant increase in connection speed, fiber optic networks offer a tremendous capacity to keep up with any new technological advances. Once the basic fiber optic infrastructure is in place, it can be rearranged and the end point electronics upgraded when necessary, to deliver even higher capacity. It can do this far more effectively than existing wireless or copper based systems.

In terms of its serviceable lifetime, glass (from which fiber optic cable is made) is long lasting, stronger than copper and more able to retain its transmission properties after physical stress such as weight strain, or even attack by rats and cockatoos. We install fiber differently from copper: in good quality coatings, inside ducts, or in the case of newer systems, encased entirely by electrical transmission wires.

For applications where signal security is a concern, fiber optic technology is an excellent solution. Fiber optic cables do not generate electromagnetic fields that could be picked up by external sensors. It is also more difficult to 'steal' signals by spicing into optical fibers than it might be with conventional copper wiring.

Shielded vs. Unshielded Twisted-Pair Cable

As we all know, the advantages and disadvantages of shielded and unshielded twisted-pair cable are under debate for a long time. Advocates of STP cable, which includes screened twisted-pair and foil twisted-pair cables, claim that it is superior to UTP cable. Shielded versus unshielded twisted-pair cable, which is the winner? This post will give you the answer.

STP and UTP cable differ in design and manufacture. But their purpose should be the same--to provide reliable connectivity of electronic equipment. In theory, both types of cable should do this equally well. The true test comes when you look at how each of these cable types performs that task within its respective end-to-end system.

Shielded Twisted-Pair Cable

Shielded twisted-pair cable encases the signal-carrying wires in a conducting shield as a means of reducing the potential for electromagnetic interference. How effective the shielding is depends on the material used for the shield--its thickness and frequency, the type of electromagnetic noise field, the distance from the noise source to the shield, any shield discontinuity and the grounding practices. Also, crosstalk and signal noise can increase if the effects of the shield are not compensated for.

Some STP cables, for example, use a thick braided shield that makes a cable heavier, thicker and more difficult to install than its UTP counterpart. Other STP cables use only a thin outer foil shield. These cables, known as screened twisted-pair cables or foil twisted-pair cables, are thinner and less expensive than braided STP cable; however, they are not any easier to install. Unless the minimum bend radius and maximum pulling tension are rigidly observed when these cables are installed, the shield can be torn.

Unshielded Twisted-Pair Cable

Unshielded twisted-pair cable does not rely on physical shielding to block interference. It relies instead on balancing and filtering techniques using media filters, baluns or both. Noise is induced equally on two conductors and is canceled out at the receiver. With properly designed, manufactured and installed UTP cable (like CAT6 UTP cable), the network is easier to maintain than one in an STP cable plant, with its shielding continuity and grounding issues.

UTP cable has evolved during the years, and different types are available for different needs. Basic telephone cable, also known as direct-inside wire, is still available. Improvements over the years--variations in the twists or in individual wire sheaths or overall cable jackets--have led to the development of Cat3 cable that is compliant with the Electronic Industries Association/ Telecommunications Industry Association-568 standard for transmission rates up to 16 megahertz. Cat 4 UTP cable is specified for signal bandwidths to 20 MHz, and Cat5e UTP cable for specifications to 100 MHz--and possibly higher.

Shielded vs. Unshielded Twisted-Pair Cable

Since UTP cable is lightweight, thin and flexible, as well as versatile, reliable and inexpensive, millions of nodes have been, and continue to be, wired with this cabling medium. This is especially true for high-data-rate applications. For best performance, this UTP cable should be used as part of a well-engineered structured cabling system.

If STP cable is combined with improperly shielded connectors, connecting hardware or outlets, or if the foil shield itself is damaged, overall signal quality will be degraded. This, in turn, can result in degraded emission and immunity performance. Therefore, for a shielded cabling system to totally reduce interference, every component within that system must be fully and seamlessly shielded, as well as properly installed and maintained.

An STP cabling system also requires good grounding and earthing practices because of the presence of the shield. An improperly grounded system can be a primary source of emissions and interference. Whether this ground is at one end or both ends of the cable run depends on the frequency at which a given application is running. For high-frequency signals, an STP cabling system must be grounded, at minimum, at both ends of the cable run, and it must be continuous. A shield grounded at only one end is not effective against magnetic-field interference.

The length of the ground conductor itself can also cause problems. If it is too long, it no longer acts as a ground. Therefore, because specific grounding requirements depend on the application, a general grounding policy that ensures the best results for an STP cabling system is not possible.

UTP cabling doesn’t have this problem. While an STP cabling system is dependent on such factors as physical continuity of the cable shield or installation with adequately shielded and grounded components, a UTP cabling system inherently has fewer potential trouble spots and is much easier to install.