OM1 vs. OM3: Understanding the Differences and Making the Switch
In new builds, selecting OM3 fiber over OM1 and OM2 fiber should be an obvious choice, even for applications with low data rates, such as building management systems, security systems, environmental monitoring, etc. Compared to OM1 and OM2, OM3 fiber supports emerging technologies and helps you establish future-ready conditions.
But choosing between OM1, OM2 and OM3 isn’t a decision limited to greenfield projects. To support modern requirements, many existing environments are faced with needing to augment their legacy OM1 fiber cable plants.
For example, high-rise buildings need to update their building management systems to support more IoT integration. Wastewater treatment plants want to bring in more automation. Rail trackside control systems need to improve reliability.
Because these environments can be decades old, they often have extensive OM1 infrastructure already in place. As a result, the people making infrastructure-related decisions—whether they’re a facilities manager, plant manager, network specialist or engineer—tend to request more OM1 to augment their cable plants without considering other options.
While there are many reasons they make this request, this is what we often hear:
- “We’re comfortable with OM1.” Users are familiar with it, have used it for years and know what to expect from OM1.
- “Our infrastructure performs adequately as-is.” OM1 meets the requirements of their current application, so there’s no big incentive to upgrade; OM1 seems sufficient
- “Our existing infrastructure won’t work otherwise.” There’s worry about existing OM1 connectors, transceivers and other infrastructure not working with OM3 since they were designed for OM1.
- “We’re worried about safety.” OM1 fiber typically uses LEDs, while OM3 fiber uses VCSELs (vertical-cavity surface-emitting lasers). Some fiber users have expressed fear about using lasers vs. LEDs for safety reasons.
- “We’re concerned about insertion loss.” Users fear that the difference in core sizes (62.5 microns for OM1 and 50 microns for OM3) won’t work together, causing insertion loss and performance degradation. When a larger core connects with a smaller core, the light from the cable with the larger core overfills the cable with the smaller core. This can cause signal loss and impact performance.
Insertion loss: does it always matter?
While some of these concerns are valid, others—especially those related to the performance of the fiber—aren’t always worth worrying about, depending on your application. Let’s consider an example.
It’s true that connecting OM1 (with a fiber core of 62.5 microns) to OM3 (with a fiber core of 50 microns) can lead to significant insertion loss. This happens as a result of the larger core “overfilling,” which we mentioned above. The light source emits light that exceeds the diameter of the fiber core and, as a result, the light isn’t transmitted efficiently. This loss happens when one fiber connects to another (a transition between fiber types). Typically, this loss is between 0.75 dB and 1 dB per connection/splice.
While the industry views insertion loss as something to avoid, its impact depends on the application. In other words, insertion loss isn’t always something you need to worry about. For instance, if you’re dealing with low-speed applications and systems, then absorbing loss as a result of one connection doesn’t impact performance. If there’s more than one connection, however, then insertion loss may be a concern in low-speed applications. That’s when you refer to the application tables in ANSI/TIA-568. These tables show you the maximum allowable insertion loss for each connection.
Knowing your loss budget is crucial to determine whether insertion loss is something you need to worry about. A loss budget determines how much optical power loss your fiber channel can have while still maintaining expected performance.
Why upgrade to OM3?
OM1 and OM2 have served their purpose very well over the last several decades, but they’ve entered their golden years.
At some point, your legacy OM1 cable plant will need to be replaced due to bandwidth, distance and compatibility limitations. Turning to ANSI/TIA-568’s application tables once again, you’ll see that OM1 and OM2 can’t support high-speed applications.
OM3 fiber exceeds OM1 and OM2 fiber across all performance parameters: insertion loss, attenuation, model dispersion, etc. OM1 and OM2 fiber also have longer lead times and can be costlier. Because they’re older technologies, they’re less commonly deployed in modern installations. This means lower production volumes, which leads to lower inventory and scarcer availability. The result: longer lead times and higher costs.
Take a phased approach to fiber upgrades
If you have an OM1 cable plant, migration to OM3 doesn’t have to happen now, and it doesn’t have to happen all at once. You can gradually migrate to OM3 while keeping portions of your OM1 network intact.
If your loss budget allows it, you can begin this migration by mixing OM1 and OM3—without worrying about the consequences of overfilling.
In most situations, migrating from OM1 to OM3 is a choice worth considering. Belden is here to help you calculate and control your loss budget so you can determine whether this phased approach to upgrading will work for you. Because every situation is different, we can’t offer advice here that works everywhere. But we can work with you one-on-one to determine what’s possible in your environment, how mixing OM1 and OM3 will change fiber testing requirements, etc.
Related links:
Belden’s New Fiber Technology Center Enables Continued Fiber Leadership and Innovation
Managing Fiber Projects Begins with Your Fiber Playbook
Create Your Own Fiber Playbook to Design, Install & Manage Fiber