Answers to common questions about fiber optic systems

Being familiar with how fiber optic systems work means getting back to the fundamentals so you can make smarter technology decisions. 

But I’ve noticed that questions about the basics come up often, no matter how experienced someone is. When I joined Belden a few years ago after working in the power distribution industry, I quickly realized that even seasoned professionals can benefit from clear, straightforward answers to foundational fiber questions.   

That’s why I put together these insights, based on presentations I often give to industry professionals to make it easier to understand what fiber really is. 

How are fiber optic systems different from copper?

While copper cables transmit data using electrical signals, fiber uses light. By transmitting data as pulses of light rather than electrical currents, fiber optic cables eliminate many of the limitations associated with copper cables, such as excessive heat generation, concern about bundle sizes, signal degradation over distance and susceptibility to electromagnetic interference.

These limitations can become issues in certain high-speed, high-density environments. But fiber is designed to overcome them. Because it transmits data as pulses of light (and at the speed of light), it can carry more information much faster and over longer distances. And because it’s immune to electromagnetic interference and uses glass instead of metal, it offers minimal signal loss. Signals remain strong and clear.

One important consideration to note, however, is that fiber has its tradeoffs, just like any technology: It can’t transmit power like copper cables can. Today, it can only transmit data.

How do fiber optic systems work?

A fiber optic cable sends pulses of light (data) through thin strands of glass “fibers.” The heart of a fiber is its glass core, which sits in the middle of the cable, giving light a path to travel down the cable to a receiving device. Data travels quickly through the fiber by bouncing along the core.

The core is surrounded by:

• Cladding, which is a layer of glass that surrounds the core and contains light pulses to prevent loss
• Coating, which prevents scratching and other physical damage
• Buffer, which provides more protection and makes the fiber easier to install
• Armoring, which protects against damage from crushing, bending and harsh environmental conditions

These inner components are enclosed inside a jacket, which protects everything inside. The type of jacket determines which environments the cable can withstand.

The cable’s construction allows the fiber to bend and rotate without snapping

What’s the difference between singlemode and multimode fiber? 

Fiber optic cables are categorized into two groups: singlemode and multimode. Each features a different core size to support different transmission distances and bandwidths. 

• Singlemode has a small core that allows a single path (mode) for light to travel through. It’s designed to transmit data across long distances (up to several miles) with little signal loss. These cables are usually yellow in color.
• Multimode has a larger core that allows multiple light paths (modes) to travel through the cable at the same time. It uses either LEDs or VCSELs (vertical-cavity surface-emitting lasers) as light sources. Multimode fiber is ideal for distances of up to a few hundred meters. These cables are usually aqua or erika violet in color. 

These cables can be joined in one of two ways:

• Mechanical splicing “holds” the fiber ends together with a special connector
• Fusion splicing “fuses” or “welds” the fiber ends together using an electric arc

What’s the difference between fiber connectors?

To connect fiber optic cables, there are several types of fiber connectors to choose from. 

• LC (lucent connector or little connector) connectors are common today, especially in high-density environments like data centers. Because they’re small, cost-effective and easy to install, they are widely used.
• ST (straight tip) connectors are one of the oldest types of fiber connectors, often found in legacy installations. Made of metal, they’re not suitable for today’s high-density environments, but they are still being used in older systems.
• SC (subscriber connector or square connector) connectors are slightly larger than LC connectors but are still very popular due to their reliability.
• MPO (multi-fiber push-on) connectors are newer connectors made for high-density applications, connecting up to 12 fibers through a single plug.
• VSFF (very small form factor) connectors are ultra-compact connectors that allow for more connections in smaller spaces. 

How are fiber optic cabling systems managed? 

In copper systems, components like patch panels are used to organize, protect and manage connections.  

In fiber systems, connections are managed with cassettes and frames. 

Frames are centralized hubs that connect and route fiber cables. Connectors can be plugged into the front and back of a frame, and frame options range from simple adapter plates for basic connectivity to more advanced optical distribution frames (ODFs), which are entire cabinets built for high-capacity, high-density environments. 

Cassettes combine frames and splice trays, housing spliced fibers to maintain proper bend radius and protect connectors. They’re easy to patch in and out. 

Making the right fiber optic system connections

While these questions might seem straightforward, they come up often when discussing fiber optic systems. Having a solid grasp of the basics will help ensure that your network connections are reliable and future-ready. 
 

Have questions about fiber optic systems that we didn’t cover in this list? Send us a note; we’ll be happy to answer them!

Get answers to your fiber questions.

Related links:

• How Our Fiber Technology Center Drives Advancement and Innovation
• How to Know When to Use Fiber Optic Cable
• Managing Fiber Projects Begins with Your Fiber Playbook