What Are The Critical Decisions Involved In Designing Fiber Optic Networks?

There are many decisions that need to be made during the fiber network design phase. However, these decisions can be grouped into higher-level buckets that make it easier for operators to prioritize.

The Primary Goal

First and foremost, operators need to have a clear sense of the overarching purpose of a new network. Nearly all critical design decisions flow from this point.

Fiber networks can be designed for long-distance or same-site communication. Long-distance communication is primarily supported by outside plant networks which can carry signals across hundreds or thousands of miles. More and more, outside plant networks are delivering digital information directly to homes or commercial buildings as fiber optic technology has grown more sophisticated and cost effective.

Premises networks, on the other hand, are used for short-range communication and often support computer networks, security systems, and other similar applications. In these networks, it is still common to see copper and coaxial cables as the primary medium through which signals are transmitted.

Once the primary goal is established, operators can choose which communication system they will support and what transmission equipment is needed.

Financial Success

Fiber operators and network owners must define “financial success” for the proposed network development. In addition to calculating projected CapEx and OpEx, it’s important for those involved to have a sense of what revenue and profit per customer they need to achieve an attractive return on investment.

Additionally, calculations should factor in the time horizon needed to recoup upfront costs. Even if a network runs profitably from year to year, it may not make sense to move forward with a project that will take more than 20 years to breakeven. Overall, there are many different financial calculations and strategies that operators can use to qualify their project before investing significant time or money.

Transmission Equipment

The two biggest factors when it comes to choosing transmission equipment are distance and bandwidth. It’s crucial to know both how far and how fast a network needs to carry signals to end users.

During this step, it’s important for operators to engage with the network owners and manufacturers to ensure that the right equipment is selected for the intended design. Equipment decisions vary drastically depending on if operators are preparing to support long, undersea routes or short links in dense cities or campuses.

Network Layout

Next, operators can start to think about the actual layout of their networks.

To start, designers should create both a high-level and low-level view of the proposed fiber network. The high-level design is intended to paint an overall picture of the architecture, signal flow, and relationships between crucial components. It also helps estimate costs before diving into the nuances of the network. The low-level design adds a layer of detail to the high-level design and defines the logic that will drive the individual components.

With the theoretical designs built, designers can then move to drawing layouts that correspond to real geographic areas. The physical landscape, natural or built, has a major impact on how cables are installed. Operators should consult with architects, building managers, and engineers to obtain architectural drawings for any infrastructure through which cables will run.

It is not uncommon for larger networks to require multiple types of cable placements in order to cover wide areas. Fiber may need to run underground, along roads, over telephone poles, underwater, or through conduits depending on the local geography.

At this stage, operators should also decide whether their network will be active or passive. Active networks manage signal distribution “actively” using electrically powered switching equipment. Passive networks rely on optical splitters to send signals where they need to go.

Although operators can make a lot of progress with digital planning and mapping, they should also make on-site visits, travel along proposed cable routes, and inspect buildings. Doing so enables them to see obstacles that may not be obvious otherwise.

Additionally, some local entities may have useful information on where pathways or conduits exist for other cables. Visiting local professionals can lead to insights that could save time and money on unnecessary construction.

When designing the actual layout of a network, it’s helpful to have a GIS platform capable of mapping geological data, such as roads, buildings, and local landscapes, alongside potential cable routes. That way, it is easy to visualize networks in the environments in which they will actually exist.

Regulatory Requirements

Before breaking any ground, operators should conduct utility research and ensure they can legally place cable and build out their desired network infrastructure. Some governments may prohibit or restrict certain types of fiber network developments.

Next, operators need to obtain all necessary permits, permissions, easements, and inspections. Every market is different, which is why it is helpful to have professionals on the team who fully understand the regulatory nuances in the area. Operators should also reach out to agencies that have information regarding power lines, gas lines, and other hidden infrastructure that could cause harm to personnel if impacted during installation.

Many local governments enforce a “Dig Once” policy, which encourages operators to install excess cables during initial installations. Doing so reduces future construction and disruption, especially in dense metropolitan areas. Operators should plan for future growth along their networks and place enough cable to support in-market expansion.

Network Components

Once operators feel comfortable with their routes and have thoroughly vetted the build area, they are ready to select network components.

The type of cable needed depends on the design and installation approach. For example, if a developer decides to install cables in conduits underground for an OSP network, he or she needs cables that can withstand high pulling tension, especially for longer routes. If cables are going to be buried directly in the ground, they should be armored and capable of withstanding high pressures, animal biting, and sharp rocks.

With aerial installations, cables need to be securely fitted to telephone poles. The method by which cables are secured depends on the specific situation and what other wires may already exist along the route. For underwater installations, cables should have strong and sealed external layers that can exist without degrading for many years.

Cables for premises networks are typically distribution or breakout cables. Distribution cables are smaller in diameter and hold more fibers. However, they must terminate inside wall boxes or patch panels. Breakout cables are better suited for industrial applications and can make direct connections without any hardware.

For each of these installation approaches, operators must also choose corresponding splicing and termination hardware.

It is highly recommended that fiber network operators create materials lists consisting of all components and conservative quantities for the entire network. These lists are used to estimate material costs and provide installation teams with a full summary of what is needed.

Installation & Testing

Fiber network installation involves many specialized teams and skills. The biggest challenge at this stage is coordinating all efforts effectively to ensure that everything is completed in the right order. Project managers should work with team leads to obtain conservative estimates on completion times and understand the full scope of what is being accomplished at all times.

Inevitably, there will be challenges and issues that arise. There should always be a project manager or technical expert onsite who can review installation progress. It’s also necessary to have someone who can be reached 24/7, especially since many installations are done at night.

Even with a well-planned and executed installation process, there may be equipment issues that need to be addressed. For this reason, operators should have thorough plans around testing components and evaluating overall network performance. Installation teams should also visually inspect all components to check for physical damages.

Before installation begins, project leads and network owners should specify exactly what equipment should be tested, how test results are documented, and what metrics are expected. Many projects test every individual fiber and component before installation and then conduct follow-up assessments as segments are placed. Network owners often want to see test data that proves their networks operate as expected.