How to convert dark fiber into WDM networks with Axiom

In a previous article, we discussed how the demand for optical fiber has taken off in the post-pandemic world. Service providers have heavily invested in upping fiber footprints to improve ultra broadband networks, while AI developers have ramped up optical fiber spending for AI data centers. One of the more untapped markets for optical fiber that we will explore in this article is dark fiber, which is a potential problem solver for businesses looking to build fiber networks while mitigating pricing concerns and maintaining flexibility for future upgrades. 

What is dark fiber?

In a fiber optic network, data travels through a fiber optics cable via light signals. The term “Dark fiber” is often misconstrued, but it is a colloquial term that refers to fiber optic cables that are not “lit.” So whereas an active fiber would be lit up, fiber cables that are not actively in use are simply referred to as unlit or “dark” fiber.

When building network foundations, enterprise service providers such as large telecommunication providers or ISPs will often lay fiber down in trunks instead of individual fibers. Although fiber can be expensive and require permits to install, mainstream providers often have the resources to acquire/lay fiber cables in bulk compared to a small or medium-sized enterprise.

Not all of the fiber is used immediately, however, and this is why dark fiber exists. Some internet service providers are simply laying the groundwork for future fiber expansion projects or are keeping excess fiber available as redundancies. Dark fiber can also arise from businesses over-purchasing fiber and not having the proper resources in-place to fully utilize this cabling.

What are the benefits of using dark fiber?

The existence of excess unlit fiber presents an opportunity for businesses and smaller, medium-sized enterprises to rent out unlit fiber to build their own individual networks, particularly in dense metropolitan areas. In a dark fiber network, the lessees rent the fiber but are responsible for implementing the actual network equipment/components on both ends of the fiber. All of the network equipment sans the fiber comes from their end, which means the entire network is under the lessee’s ownership.

The ability to deploy fiber networks without having to buy the actual fiber itself, helps businesses retain flexibility as they can scale their networks without over committing resources to building static networks. Because they can swap out the equipment on both ends (i.e. 10G equipment for 800G hardware), this alleviates the spending and network management concerns of having to invest in a fiber infrastructure that is locked to a specific application. Thus, the primary benefit of using dark fiber is to maximize scalability.

Networks built on dark fiber also have the added benefit of being a private network with more robust security compared to third-party managed fiber services. The reason being is that the leased optical cable is a dedicated line with restricted access to the network traffic in standard dark fiber setups. Businesses using dark fiber have complete control over their networks with increased granularity over their network and fiber routes compared to if they were to rely solely on managed services for network needs. Furthermore, fewer endpoints in a network infrastructure means fewer potential failure points in a network. 

Benefits of using dark fiber with DWDM:

High bandwidth

DWDM enables significantly increased data transmission capacity on a single fiber compared to traditional single-wavelength transmission. 

Scalability

You can add more wavelengths to an existing DWDM system as needed to accommodate growing bandwidth demands. 

Cost-effective

Utilizing existing dark fiber infrastructures can be more cost-effective than laying new fiber cables.

How to maximize the potential of dark fiber

The challenge in maximizing the potential of a dark fiber deployment is implementing the appropriate endpoint devices on each end of the fiber networks. How each business sets up their fiber infrastructures point-to-point is purely up to their needs and requirements, however, increasing bandwidth and cutting down optical complexity are generally the ways to go for maximizing the value of dark fiber.

The primary difference between DWDM and dark fiber lies in their approach to utilizing fiber infrastructure. DWDM enhances the capacity of existing fiber networks by multiplexing multiple wavelengths over a single fiber, making it a more scalable and cost-effective solution for incremental bandwidth needs. In contrast, dark fiber involves deploying dedicated fiber strands, which requires a higher initial investment in equipment but offers unparalleled control and customization options.

Some of the best fiber optic technologies for dark fiber include:

CWDM

CWDM (Coarse Wavelength Division Multiplexing) and DWDM (Dense Wavelength Division Multiplexing) solutions are ideal for dark fiber deployments. CWDM and DWDM utilize different ranges in the light spectrum, enabling transceivers to send different signals on different light wavelengths. 

DWDM

DWDM would typically be used on a core network where huge capacity is required as each pair of fibers could transmit up to 96 channels. The technology is also able to reach greater distances – up to 80km but could be as far as 1,000km with amplification of the signal.

It is a good choice for businesses dealing with large data volumes, such as eCommerce and Media, and those Service Providers who manage customers where dedicated connectivity, high bandwidth, and low latency is a must.

BiDi

BiDi (BiDirectional) transceivers also work great in a dark fiber environment as it offers bidirectional data transfer, effectively doubling the data rate. BiDi also isolates activity to one fiber, limiting the number of errors that can occur in the network.

Coherent technologies

In long-range technologies, coherent technology modulates multiple aspects of the signal to increase the signal reach in long-distance networks.

The ZR transceivers utilize PAM4 modulation schemes with Coherent technology applied, to strengthen data signals and reach to 100km or higher.

MUX

Mux solutions play an important role in WDM networks as they fuse together the individual data signals to send as a consolidated, high-capacity signal over the fiber.

ZR transceivers

High-speed ZR transceivers utilize PAM4 modulation schemes with Coherent technology applied, to strengthen data signals and reach to 100km or higher.

Axiom dark fiber ready technologies

Axiom is a leading high-performance, networking connectivity solutions provider with the ability to customize solutions based on customer needs. We offer cutting-edge technologies that are conducive to dark fiber deployments. Axiom carries the following dark fiber solutions:

CWDM

MUX/DEMUX

Transceivers

     -1G and 10G (40km and 80km)

     -25G (10km)

DWDM

MUX/DEMUX

• EDFA

• Dispersion Chromatic Module (40 and 80km)

• Transceivers

     -1G and 10G (40km and 80km) – Tunable or Fixed Channel

     -10G Tunable (100km+ unamplified)

     -25G (15km) - – Tunable or Fixed Channel

     -100G - QSFP28 – Fixed Channel

     -100G (Tunable - QSFP28 – 80km unamplified)

     -400G (ZR/ZR+ - Tunable - QDD – 80km unamplified)

BiDi

• Transceivers

     -1G to 100G different distances

10G to 100G transceivers

Coherent 100G and 400G (ZR/ZR+)

Axiom is backed by one of the most experienced, renowned engineering teams in North America with extensive experience in all things optics related. Axiom engineering and support team can help your business establish a fiber optic infrastructure for dark fiber deployments and optimize the endpoint equipment for unparalleled dark fiber performance. Axiom tests our optical equipment extensively to ensure minimal failure rate and downtime in all types of configurations. To learn more about our lineup of Axiom dark fiber offerings, contact an Axiom representative today.