Decoding 100G: A Guide to Wavelengths and Distances

In the world of high-speed networking, 100G transceivers are the workhorses driving data centers and enterprise networks. But if you’ve ever looked at a spec sheet, you know that “100G” isn’t a one-size-fits-all term. Depending on the specific standard, these modules operate on different wavelengths, over different distances, and using different channel configurations.

Whether you are upgrading a data center or planning a long-haul link, understanding the physical layer differences is critical. Here is a quick breakdown of the most common 100G transceiver types to help you match the right optic to your fiber infrastructure.

Multi-Mode Short Range (SR)

For short connections inside the rack or between nearby racks, multi-mode fiber is often the go-to.

100GBASE-SR4: Operates at 850 nm. It uses 4 parallel channels (25 Gbps each) to achieve 100G speed. This is typically used for distances up to 100 meters.

Single-Mode CWDM Solutions

For moderate to long distances, Course Wavelength Division Multiplexing (CWDM) allows multiple channels to travel over the same fiber strand.

100GBASE-CWDM4: Uses four distinct wavelengths (1295, 1300, 1305, 1310 nm). It’s designed for reaches up to 2 km.
100GBASE-LR4: Similar to CWDM4 in wavelength usage but built for longer reaches, capable of hitting 10 km.
100GBASE-ER4: The “Extended Range” version, pushing that same four-wavelength technology up to 40 km.

Single-Mode 1310nm Solutions

The 1310 nm window is a sweet spot for fiber optics, offering low dispersion. Several standards utilize this specific wavelength.

Parallel Options (Multiple Fibers):

100GBASE-PSM4: This operates at 1310 nm but, like the SR4, uses parallel fibers (4 channels at 25 Gbps). It is generally used for reaches up to 500 meters.

Single Channel Options (Newer Technology): Newer PAM4 technology allows for 100G to be transmitted on a single “lane” rather than splitting it into four 25G lanes.

100GBASE-DR: Reaches up to 500 meters.
100GBASE-FR: An intermediate option reaching up to 2 km.
100GBASE-LR: A single-channel long-reach option capable of 10 km.

Summary

Choosing the right 100G module comes down to three factors: the type of fiber you have (Multi-mode vs. Single-mode), the distance you need to cover, and your existing infrastructure (MPO connectors for parallel optics vs. LC connectors for duplex).

From the 100m hops of SR4 to the 40km reach of ER4, there is a 100G solution for every topology.

FAQs

What is the difference between a "Wavelength Service" and a "Dark Fiber Lease"?

Simply put, Wavelength Service is a “Lit” service. Therefore, we provide the fiber, the equipment (lasers, DWDM gear), and all the 24/7 management. You just plug your router into our hand-off and get instant capacity (10G to 800G).

Conversely, a Dark Fiber Lease is an “Unlit” service. Crucially, we only provide the bare fiber optic cable. You bring all of your own optical equipment, manage it, and handle future upgrades. In short, Wavelengths are for immediate capacity; Dark Fiber is for ultimate control.

Is a Wavelength Service secure? Is my traffic shared?

Yes, our Wavelength Services are inherently secure. Because they are a Layer 1 connection, your traffic is delivered as a dedicated color of light across our network. Consequently, it is physically isolated from all other customer data, including the public internet. This provides a Private Fiber Connection that meets strict enterprise and financial security standards.

What level of latency can I expect on a Wavelength Service?

Our advantage is ultra-low, guaranteed latency. First, as a Layer 1 service, we bypass all slow routing and processing layers. Moreover, for critical routes (like financial corridors), we can provide a Guaranteed Latency Service Level Agreement (SLA). Therefore, the latency is predictable and minimal, making our circuits ideal for synchronous data replication and high-frequency trading.

Can I upgrade my Wavelength speed (e.g., from 100G to 400G) without replacing the fiber?

Yes, absolutely. Because our services are based on DWDM technology, we use a single fiber pair to carry many individual channels (wavelengths). Therefore, upgrading your service (e.g., moving from a 100G circuit to a 400G circuit) often requires only swapping out the optical equipment on our end, not physically replacing the Scalable Wavelength Capacity in the ground. This makes upgrades fast and non-disruptive.

Do you offer Wavelength Services for both metropolitan (metro) and long-haul routes?

Yes, we offer complete geographic coverage. Specifically, our Metro Wavelength Service connects data centers and offices within a single city (e.g., Dallas DCI). Conversely, our Long-Haul Optical Transport connects distant cities (e.g., New York to Chicago). In both cases, you receive the same level of dedicated capacity and managed reliability.

Ready to Discuss Your High-Capacity Network Requirements?

Don’t let bandwidth limitations slow your business. Our network engineers are ready to design a custom DWDM solution tailored to your specific endpoints and capacity needs (from 100G up to 800G).