What is Lit Fiber and Dark Fiber

Everybody knows that what are fiber optics cables and types of fiber optic cables. Do you know that this category of cables can be divided based on their usage also? That is what we will speak in this article where categories are Lit fiber and Dark fiber. The simplest way of definition for this is that the fiber optic cables that are actively used for data transfer are called as Lit fiber and fiber optics cables that are already laid on the ground and ready to use, however, there is no active data transfer through this cables are known as Dark fiber. It’s really necessary to understand the evolution, usage, and requirement of these cables and how it’s created. More of this information can be found below,

Lit Fiber

When we all talk about the fiber communication aren’t we all considering only the part of fiber cables where data transfer is actively happening. These cables are generally called as Lit Fiber. A Lit Fiber service is a large bandwidth connection providing high-speed Internet or data service delivered over fiber optic lines. Lit Fiber is used by businesses that are engaged in telecommunications, wholesale Internet access, or wholesale ISP services to provide the bandwidth capacity needed for customer applications including email, file sharing, web hosting, data backup, video, VOIP, or VPN access. Lit Fiber service comes in many speeds ranging from Ethernet to DS3 to wavelengths over fiber optic lines. Lit Fiber is also known as Wholesale Carrier Ethernet, Wholesale ISP, Wholesale Internet Access, Wavelength Service, Fiber Internet, or Fiber Lit Buildings. So if you are a network guy, you can always understand that this is the service used worldwide since the evolution of fiber optics and still continue to be.

Some of the major disadvantages with lit fiber are as following,

• Your communication was completely handled through a telecommunication provider. There can be the existence of multiple types of equipment between your fiber communications(routers, switches, boosters, etc.) that can impact your communication. 

•  We have to pay per usage based on the communication provider. A carrier is making available for lease fibers themselves within an existing cable. So a particular rate & format (like "1GE interface with 300Mb/S bandwidth"). Higher the bandwidth is required higher the cost. 

•  Sometimes the addition of new fibers also required by carriers when all existing fiber connections are leased out. It may take a long time for you to wait until this is done as this activity is impacted by many external factors too(approvals, civil works, etc.)

Even though lit fiber is actively used by telecommunication providers these are generally known as the traditional way of fiber communication for enterprises due to the advantages of dark fiber connections.

Dark Fiber

Dark fiber is fiber optic infrastructure that’s not yet in use by a service carrier or a provider. It is an installation of cables currently lying dormant, ready to be connected at some time in the future. Because they literally lack the lasers that send light through the cables, we call it “dark” fiber. In other words, in fiber optic networks when data is being transmitted, light is passed through the cables. If no data is being transported, there are no light waves traveling along the cable, therefore the fiber is dark. Simple, isn’t it?

Let me tell you some of the backstories for the evolution of dark fiber concept,

Story Line 1:  

In the beginning, many telecommunication carriers had the tendency to future-proof their fiber optic networks by installing more cabling than what was actually needed for their current requirements, just to be prepared in case they will face exponential data growth. Because of this overestimation and some technological developments concerning the way data is being packed, many fiber optic networks are not used at their fullest capacities. For example the availability of wavelength-division multiplexing(WDM) technology reduced the demand for fiber cables by increasing the capacity that could be placed on a single fiber by a factor of as much as 100. As a result, the wholesale price of data traffic collapsed. Therefore, dark fibers were created to take advantage of this extra capacity. 

So isn’t it beneficial if this additional capacity to be leased out to other companies who need to have their own fiber connection? At the moment, dark fiber can be leased from the network providers and operators. Clients will use the dark fiber lines to create their own privately-operated optical fiber network. Dark fiber networks are separated from the main network and are controlled by the client.

Story Line 2: 

In Amsterdam's city wide installation of a fiber network, roughly 80% of the costs involved were labor, with only 10% being fiber. Much of the cost of installing cables is in the civil engineering work required. This includes planning and routing, obtaining permissions, creating ducts and channels for the cables, and finally installation and connection. This work usually accounts for most of the cost of developing fiber networks. It therefore makes sense to plan for and install, significantly more fiber than is needed for current demand, to provide for future expansion and provide for network redundancy in case any of the cables fail.

In both the scenario we can see that we cannot either under design the fiber cable installation due to the fact that data usage around the world is an emerging day today. As the optical technology grows more sophisticated and expands into high bandwidth optical backbone connectivity, enterprises are now turning to the private and secure dark fiber network. So in summary of both these storylines, I can say that dark fiber is one of the emerging ways of fiber communication that is adopted by many enterprises due to its various advantages.

Dark Fiber as a Networks Solution

So in dark fiber, your telecommunication carrier is making fiber cables available for lease themselves within an existing cable. They are not going to maintain your network once they lease the fiber cables to you. As a customer, you are getting an end to end physical connection of fiber cables and you have to take care of building the entire fiber infrastructure required for your communication. You then connect whatever you want to those fibers, whatever speed, whatever format, whatever wavelength - from a single simple circuit up to CWDM or DWDM systems. Dark fiber networks can be set up in a variety of ways, including dark fiber rings, point to point or point-to-multipoint configurations.

A dark fiber network requires less power and has a higher capacity, generally due to the use of DWDM (Dense Wavelength Division Multiplexing). Simply put, with DWDM, a dark fiber network can easily increase bandwidth and allow more data to be sent via optical fibers. Furthermore, dark fiber often has better signal strength and is more immune to interference than the fiber making up traditional networks. The image above shows how we can use dark fiber as the carrier medium and can achieve multiple channel traffic with DWDM as a termination point.

Why Dark Fiber?

If your company is considering utilizing a dark fiber network, there are a few things you should bear in mind. First, make sure you buy dark fiber for the right reasons. Most companies adopt a dark fiber network because of the premium advantage of the service itself—unlimited, scalable bandwidth. By the utilization of dark fiber, enterprises can upgrade bandwidth they need by changing out equipment interfaces themselves, without notifying the carrier or worrying about term liability on a leased circuit. That’s a good option for companies whose bandwidth needs can change rapidly or unpredictably for point to point connectivity. Furthermore, with dark fiber, a client can expect to get high levels of performance, a highly secure network, and superfast speeds just as you can see in the following chart(Mostly customers are using dark fiber with a combination of these multiple technologies).

But buying dark fiber is not like buying other telecom services because it’s more like a physical asset than a service. The fiber itself must be maintained and repaired when there are problems like fiber cuts, and these outages are typically much longer than other services, so you should be careful to negotiate acceptable SLAs for these repairs. Long-haul dark fiber, in particular, is complicated because it requires optical regeneration or amplification. This means you have to figure out how to remotely monitor and maintain that equipment, which, depending on the route, could be in far-off and difficult to access locations. Of course, the cost might be the concern of utilizing a dark fiber solution. Dark fiber generally costs more upfront capital expense due to the fiber infrastructure providers’ payment terms and additional equipment required. However, in most cases, the long-term costs of a dark fiber solution may be much less than a long-term managed solution.

Dense Wavelength Division Multiplexing – DWDM (where multiple data signals are being transmitted at the same time over the same optical fiber) has been essential in the development of the dark fiber. Even if the signals are transmitted at the same time, they use different wavelengths to keep the data signals separated. DWDM helps in increasing the bandwidth and allows a bigger volume of data to be transported via optical fiber. Because of the use of DWDM, the dark networks have a higher capacity, require less power and are generally more immune to interference than traditional networks.

Ultimately, whether to employ a dark fiber solution is subject to review based on several factors. Operators must decide what solution will serve their end consumers' best interests while meeting their own capacity needs.

Advantages of dark fiber

Security

The realities of fiber optic layouts ensure a high level of physical security. Unlike public access telecom networks, with multiple public access points at various terminal and intermediate nodes throughout the network, dark fiber routes are accessible only at each of the two endpoints of the fiber run. Cutting back on the number of network access points limits the potential for malicious interference with the network, reducing the need for additional firewalls and other security measures.

Leasing or owning a dark fiber route also ensures that an organization retains control over its network. Instead of outsourcing bandwidth needs to a third party, this option allows for total control of the capacity and equipment over a private network. Tight security makes dark fiber an ideal option for those who regularly deal with sensitive information, such as healthcare organizations and financial institutions.

Reliability

When a company leases dark fiber, it is the sole user of the network. Using an in-house IT department to manage a network eliminates dependency on a provider. This means no more inconveniently scheduled maintenance, costly service upgrades or long waits for capacity increases. You’re not just another customer. You’re in control. Dark fiber is capable of providing cost-effective network redundancy in the case of a primary network failure.

Scalability

Dark fiber allows you to grow your bandwidth right alongside your business. Scaling up is quick and easy, and the available bandwidth is virtually unlimited. For example, we can say that ‘Unlimited bandwidth when the fiber is used in conjunction with WDM’. When increasing bandwidth is even an option with many carriers, it can be a lengthy process. Requests to ramp up bandwidth can take weeks. And then there’s the cost. With a carrier, bandwidth increases will more than likely result in an increased monthly fee. Bandwidth upgrades with some dark fiber providers won’t be reflected in your monthly bill.

Since leasing fiber allows companies to purchase their own equipment, customers aren’t tied to whatever devices their carrier decides to deliver. This ensures your business can be as cutting-edge as it needs to be to remain competitive.

Cost

In addition to superior performance, dark fiber often results in substantial cost savings over lit services. But installation is something organizations need to seriously consider before choosing dark fiber. Construction is sometimes required to reach certain locations. Knowing the location of the fiber providers existing network will provide a better understanding of the size of the undertaking. While laterals and last mile connections may represent significant investments upfront, dark fiber offers the promise of strong ROI for companies that use a substantial amount of bandwidth.

Conclusion

To sum up, lit fiber and dark fiber have its own advantage and we can say that both of these are having its own future. Technology needs have changed over time. Enterprises have become more dependent upon cloud services, interconnected infrastructures have grown in number, and massive growth in the Internet of Things (IoT) all require a large data communications infrastructure that can scale rapidly, predictably, and on demand. To fulfill these needs, dark fiber providers have entered the market and are working to provide massive bandwidth, low latency, and high quality connectivity to the end customer in the form of raw glass: dark fiber. It can be the right solution for many of today’s high-bandwidth enterprise connectivity, but make sure you go into it with a full understanding of its advantages and disadvantages. 

Knowledge Credits: www.opticalfiberalsa.over-blog.com, www.archfibernetworks.com

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