What to Consider When Selecting Fiber Optic Cable


When introducing fiber optic cable into your Ethernet network, determining which equipment you need may seem to be a straightforward activity. You determine the distance of your fiber run and choose a device that has a distance specification within that range. However, there are several underlying factors that you need to consider to ensure the system will work, including:

  • Fiber modes: Singlemode and multimode (fiber core sizes) are the two fiber modes.
    Fiber launch power: the power output by the transmitter. Launch power is measured in dB.
  • Receive sensitivity: the range the receiver can accurately read incoming light pulses from the transmitter. Receive sensitivity is also measured in dB.
    Fiber cable attenuation: the loss incurred over the length of the fiber cable run. Also measured in dB.
  • Fiber budget: the difference between the transmitter launch power and receiver receive sensitivity. Fiber budget indicates the amount of loss incurred that if exceeded will cause a loss of communication.

It is extremely important to understand each of these factors when planning a fiber project because vendor distance specifications are based on standard dB loss across fiber, with either an aggressive or conservative skew depending on the company. In other words, a vendor’s distance specification uses the fiber budget to come up with a guess of the distance that can be achieved. The vendor’s guess cannot take in every variable in your project, as each fiber installation is unique: The way the fiber is run, the number of splices, the cleanliness of the connectors, all of these factors and more will have an effect on the distance a signal will travel. To ensure a system will work, an actual measurement of dB loss over a fiber run should be taken and compared to the stated link budget of the equipment being used. To take this measurement, use a light source and a power meter to determine the attenuation (insertion loss), length, and polarity. This measurement will help ensure that the equipment you use will have the appropriate launch power and receive sensitivity to work on that fiber run. A vendor's estimate is no substitute for an actual measurement.

A call to Black Box Support will ensure you get the correct equipment for any fiber-networking project.

Fiber Advantages

The use of fiber is becoming more ubiquitous due to the following factors:


Fiber only loses 3% of the signal over distances greater than 100 meters, compared to copper's 94% loss of signal.


Fiber optic bundles do not conduct electrical currents, making fiber data connections fully resistant to fire, electromagnetic interference, lightning, and radio signals. Copper cables are designed to conduct electricity, making copper internet vulnerable to power lines, lightning, and deliberate signal scrambling.


Copper uses electrons for data transmission, while fiber uses photons. Light is faster than electrical pulses, so fiber can transmit more bits of data per second and offer higher bandwidth.


In an era of increased attention toward cybersecurity, fiber optic internet is touted as a cost-effective way to instantly increase your network protection. Copper cable can be intercepted by connecting taps to a line to pick up the electronic signals. Putting a tap on a fiber optic internet cable to intercept data transmissions is incredibly difficult. It's also easy to quickly identify compromised cables, which visibly emit light from transmissions.

Cable Size

Fiber cable's speed is not connected to its size, and it's far lighter weight than copper. This renders it easier to use and less demanding of space in small rooms.


Investing in fiber internet will cost more than copper in the short term, though costs are drastically decreasing as this option becomes more commonplace. Ultimately, the total cost of ownership (TCO) over the lifetime of fiber is lower. It's more durable, cheaper to maintain, and requires less hardware. The advantages of fiber make it overall, a more cost-effective investment for organizations of all sizes.


Copper cable is a relatively delicate technology. Typically, it can sustain about 25 pounds of pressure without being damaged. This means copper cable can be stressed or compromised with relative ease during routine operations in a company's telecommunications space, such as installing cable runs, any change or move, and installing new equipment. In contrast, fiber can withstand about 100 to 200 pounds of pressure, meaning it is far less likely to be damaged during routine operations in close proximity.

Not sure what you need for your next fiber cabling project? Contact Black Box today for help. We can ensure you get the correct equipment for any fiber networking project.

About the Author

Dave Sefzik

Dave Sefzik has 30+ years’ experience in the Networking and Datacom industry, serving 7 years in the U.S. Army Signal Corps as a COMSEC Repair and Communication Systems Installer before his time at Black Box. For the past 25 years, Dave has assisted Black Box customers in various roles, offering presales and post-sales support for 10 years before transitioning to Product Engineering for Networking and Datacom. Today, Dave is responsible for product compliance and quality control. He ensures products meet their performance criteria and teaches the internal engineers and sales team about technology.


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