Dark Fiber Gives You Control

By: John Shepler

Higher and higher bandwidths are expected in business IT infrastructure. That includes the local networks and leased lines for metro and wide area bandwidth. It’s about more than that, though. Just as important are parameters such as latency, packet loss and jitter. Security is a major concern for all network operations. Finally, the ability to make changes, create workarounds and rapidly bring resources online are important to keeping network operations running smoothly.

Big Bandwidth Means Big Pipes
The need for increasing bandwidth has resulted in a mass migration from copper wirelines to fiber optic cables. Copper may still make sense to the desktop, but outside network connections need the capacity of fiber.

Fiber leased lines are available from 10 Mbps to at least 10 Gbps, with 100 Gbps service becoming more readily available. They can be configured as point to point dedicated lines or dedicated Internet access. Many companies need some combination of the two. The Internet is essential to communicating with customers and suppliers. Direct lines to cloud service providers and between company facilities provide more consistent performance, lower latency and higher security.

Wavelengths are Like a Private Fiber Link
Fiber optic cables are said to have unlimited bandwidth. While that might seem like an exaggeration, in practice it is pretty hard to run out of bandwidth. Each cable has multiple fibers, sometimes as many as 100 in a bundle. Each of those fibers can carry multiple streams of non-interfering data through a process of wavelength division multiplexing.

There are two schemes. Coarse Wavelength Division Multiplexing can divide the fiber into a dozen or more laser colors called Lambdas, all traveling the same time. Dense Wavelength Division Multiplexing ups that count to 80, 96 or more separate wavelengths using more sophisticated equipment.

Note that each wavelength acts like its own fiber. It is unaware of other wavelengths on the same strand. When you lease a wavelength your data is not multiplexed with anyone else’s. You have exclusive use of all the bandwidth on that wavelength, which might be as high as 10 Gbps. Need more bandwidth? Lease another wavelength. Until the fiber bundle is fully loaded, you’ll never have to run more cable.

Dark Fiber Gives You Ultimate Control
What’s better than a wavelength? Having the entire fiber to yourself. That sounds great until you think about the cost of running your own fiber. It makes total sense on your own property, but what about connections across town or across the country? Unless you are in the business of providing carrier services, you’ll find trenching your own fiber to be cost prohibitive.

There is a way to get pretty much your own fiber. Lease an unused strand from a service provider. That’s more doable than you might think. Remember that it doesn’t make sense to go to all the trouble of burying a single fiber strand when you can bury a multi strand cable or even multiple multi strand cables for not much more cost. That way, a carrier only has to lay in the fiber once and have capacity to spare for decades.

These unused strands are called “dark” fiber because there is no laser light illuminating them. It could be your job to light the fiber. The carrier will simply give you access at each end of the fiber and the rest is up to you.

Clearly this beyond the capability of smaller companies, but they are likely well served by lit fiber options already available. Larger and more sophisticated IT organizations may be able to make good use of dark fiber for research labs, medical campuses, video content creation and transport, engineering & manufacturing, and other demanding applications.

Benefits of Dark Fiber
Owning exclusive rights to use an entire fiber is the next best thing to building your own. You do need to provide the termination equipment at each end and manage those resources. That may include your own DWDM equipment to generate multiple wavelengths for all the bandwidth you can reasonably use.

Without competing customers, there is no need for multiplexers to add and drop connections along the route. The fiber serves your locations only. The lack of unnecessary equipment in the line minimizes latency. Unlike the Internet there is no need for routers every so often to direct traffic. You not only have minimal latency, there is no reason it should vary from common carrier routing decisions, and no congestion as long as you are not overloading the capacity of the fiber or individual wavelength.

Security is another big benefit of dark fiber. There is no sharing of bandwidth among customers. This is similar to the old “nailed up” copper private point to point line. You need to trust the operator of the fiber, but don’t have to worry about the other customers. Of course, encryption on top of dedicated fiber gives you the most security you’ll get in point to point transmission.

Dark Fiber Availability
As fiber is being extensively deployed for Internet, cable television, and cellular towers, dark fiber is also becoming more and more available. Competitive fiber network operators and some cable system operators have lots and lots of extra capacity installed. They are more than happy to lease out unused strands when there are dozens sitting dark.

Do your needs demand the capacity, flexibility, and security that dark fiber offers? Find out what dark fiber options are available for your business locations.

WDM Wavelength Services Offer Expandability

If your need is for high bandwidth, security and flexibility, you should take a look at wavelength services. This is more than the typical fiber optic bandwidth service. It’s almost like owning the network facilities yourself.

The thing about fiber optic transmission is that it offers almost limitless bandwidth. That’s a foreign concept to anyone who’s been tied to copper wireline services. It’s also an odd notion for those who pick a fiber optic service level and sign a contract for it. If you order OC3 SONET service, what you get is a line that runs at 155.52 Mbps with a payload of 148.608 Mbps. You don’t have to fill the pipe continuously, but the capacity is there all the time. If you need more bandwidth, you only recourse is to add an additional service or upgrade to something like OC12 or Gigabit Ethernet.

What you are using with fiber optic services is not the entire bandwidth of the fiber. In fact, you may be totally unaware that your signals are multiplexed with lots of others all traveling on the same fiber strand. If there is only one laser beam with a single color or wavelength shining through that fiber, it likely has a capacity of at least 10 Gbps. Chances are, though, that there are many different color beams all riding simultaneously down the fiber. They don’t interfere because they are different colors of light, called Lambdas, all in the infrared region of the spectrum. Each Lambda or wavelength has a carrying capacity as high as 10 Gbps. You can think of these as equivalent to individual high capacity lines. If the fiber optic strand were made of copper, each wavelength would be a separate pair of wires.

What if you could lease a wavelength instead of a copper wireline or a fixed bandwidth service on a fiber optic cable? The wavelength doesn’t care what modulation or data pattern you use. It’s just a pure light beam of one wavelength. There’s no fancy footwork required to convert between one protocol and another just to be compatible with what’s running on the line. That opens some interesting possibilities. You could use your leased wavelength to carry Gigabit Ethernet or Fast Ethernet, SONET OC3, OC12 or OC48, Fibre Channel, or ESCON.

Need to transport a variety of high bandwidth protocols? OK. Just lease multiple wavelengths and give each protocol its own Lambda. The won’t interfere. In fact, they won’t even known the other wavelengths exist.

This type of network transport is no longer a pipe dream. All you need to do is lease WDM Wavelength Services from a fiber optic network carrier such as AboveNet. What AboveNet has done is install a base of dark fiber in many metropolitan areas. It’s called dark because it hasn’t already be put into service with a particular fiber optic service in mind. It’s like a blank canvas ready to become any work of art. AboveNet “lights” the fiber as needed using WDM equipment to create their wavelength services.

WDM stands for Wavelength Division Multiplexing. It’s the technology that creates multiple wavelengths on a single fiber strand. This is a standardized process that ensures there is enough separation between the wavelengths that they won’t interfere and that different brands of networking equipment will work together. There are two flavors of WDM: CWDM or Coarse Wavelength Division Multiplexing and DWDM or Dense Wavelength Division Multiplexing. The difference is that DWDM squeezes more wavelengths, up to 160, onto a given fiber but at a higher cost than CWDM.

Is this affordable? AboveNet says that their CWDM service becomes competitive at the OC-3 service bit-rate. If you can use more bandwidth than that, you’ll save money with CWDM. Typical applications include connecting corporate headquarters with branch offices and data centers, or connecting multiple hospitals and medical centers for exchange of medical images and other health service records.

Has your business or organization become limited by the network services available? Perhaps it’s time to move up to wavelength services. Find out by getting prices and availability of fiber optic wavelength services for your locations. Complementary consulting by bandwidth experts is also available for serious applications.



Note: Image of light spectrum from prisms courtesy of Marcellus Wallace on Wikimedia Commons.

Wavelength Services For The Enterprise

Once needed only by telecom carriers, wavelength services are now available for enterprise users. These higher bandwidth fiber optic services are needed by hospitals, medical centers, banks, financial institutions, service providers to government, video production and distribution houses, content delivery networks and research facilities. Every day more applications cross that threshold of needing faster pipes to transfer data. Should those faster pipes be wavelength services?

A wavelength or lambda is light at a particular frequency or color. This characteristic is generally expressed in terms of wavelength in nanometers rather than frequency in terabits per second. Just as frequencies can be multiplexed to create a broadband wireline service, wavelengths can be multiplexed to offer multiple paths through a single fiber strand.

The multiplexing process at the physical level for fiber optics is called WDM or Wavelength Division Multiplexing. There are two technologies available. CWDM or Coarse Wavelength Division Multiplexing creates anywhere from 2 to 20 independent wavelengths, with 16 being a standard. DWDM or Dense Wavelength Division Multiplexing requires more precise equipment to create from 40 to 128 or more independent wavelengths.

As you can imagine, having dozens of independent wavelengths per fiber optic core and perhaps 100 cores in a cable, the amount of available bandwidth is truly staggering. So much so, that carriers are leasing out entire wavelengths to companies and organizations that need high bandwidth conduits. Wavelength services are similar to point to point T1 lines in that you have exclusive use of the wavelength. While the wavelengths in any particular core may be leased by dozens of different users, any multiplexing on the particular wavelength you are leasing is up to you. It's a private line service, with the line being a particular wavelength of light.

What bandwidths are available on these wavelength services? Commonly available speeds are 2.5 Gbps and 10 Gbps. Other increments of 1 Gbps and 5 Gbps are also increasingly available. Need more than 10 Gbps? It's possible to get as much as 40 Gbps in some areas. Can 100 Gbps be far behind?

Another advantage of wavelength services is that they are not locked into a particular protocol. You can use your wavelengths to transport Fast Ethernet (100 Mbps), Gigabit Ethernet, SONET OC-3, OC-12, OC-48, Fibre Channel, ESCON and Frame Relay.

Who's offering wavelength services suitable for large enterprise and other organizational use? Major competitive carriers such as Level 3, XO Communications and AboveNet have these and other fiber optic bandwidth services available right now. If you have a serious application that needs connectivity at this level, find out what wavelength services are available for your business locations.

Many Wavelengths to Serve You

What happens when you max out the capacity of your network but still need more bandwidth? You have to go with a faster network, right? You may have to go with faster NIC (Network Interface Cards) and Ethernet switches for every node. What you don't want to do is run out of capacity on your lines. When you've got all you are going to get out of your structured wiring system, it gets expensive, really expensive, to upgrade that network. But what if you could just add some more signals into those same cables and multiply the bandwidth 32 or even 160 times? If your network is fiber optic based, you can do just that.

The magic is in a process called WDM or Wavelength Division Multiplexing. We think of fiber optic networks as having a beam of light at one end and a receiver at the other. The transmission electronics modulates a laser beam with our data stream and a photodiode at the other end converts the modulated light back into electrical pulses. What WDM does is send multiple beams down the same fiber optic cable in parallel. Two beams gives you 2x the capacity, four beams gives 4x, and so on. This process is so well developed that you can send 16 to 160 separate beams simultaneously to support enormous bandwidths.

Fiber optic networks are much faster than copper-based networks to begin with. Gigabit Ethernet over copper can be a challenge within an office environment. Forget long haul. T3 is the highest of the copper T-Carrier systems at 45 Mbps and is usually only deployed over a few miles. T1 lines can reach out to just about any distance using regenerators, but the bandwidth is limited to 1.5 Mbps. Compare that to typical long haul fiber bandwidths of OC-48 at 2.5 Gbps or OC-192 at 10 Gbps. Some carriers are upgrading their core rates to the OC-768 level of 40 Gbps.

In the world of copper transmission lines, frequency division multiplexing (FDM) is the equivalent of fiber optic WDM. FDM is what Cable TV companies use. Each channel has its own carrier and occupies its own narrow band of frequencies in the spectrum. More than 100 standard TV channels of 6 MHz each can be carried on a typical cable system. Some of these channels are assigned to broadband Internet services rather than television transmissions.

Wavelengths are also different frequencies which, in the optical (including infrared) parts the spectrum, represent different colors. They are also called lambdas after the Greek letter representing wavelength. Light split from a prism demonstrates that many different colors can exist simultaneously in a single beam without interference.

There a two general categories of WDM. CWDM or Coarse Wavelength Division Multiplexing uses up to 16 different wavelengths within an individual single mode fiber strand. DWDM or Dense Wavelength Division Multiplexing uses up to 160 wavelengths in a fiber strand and requires more precisely controlled lasers. But at 10 Gbps capacity per wavelength, a system with 160 wavelengths offers well over a Terabit/second bandwidth.

WDM schemes are found in long haul carrier core networks where the cost of installing hundreds or thousands of miles of fiber optic cable far exceeds the cost of new electronics to increase capacity by adding more wavelengths on the same fiber. WDM or CWDM is also installed on dark fiber when customers need the extra capacity in metropolitan (MAN) networks.

Thanks to WDM and competitive carrier build-outs, fiber optic bandwidth is more affordable than ever. That's especially true for the new Ethernet over fiber services available to businesses in major metropolitan areas.