A wavelength is a managed optical service in which a provider dedicates one channel of light on its fiber network to you, carrying data between two locations at a fixed speed such as 10, 100 or 400 Gbps. The provider runs the optical equipment; you get a high-capacity, point-to-point link that behaves like a very long cable between your two endpoints. Wavelengths are widely used for data center interconnect, links to cloud on-ramps and colocation facilities, and other paths that need very high bandwidth with consistent latency.
At a glance
- A wavelength is a Layer 1 service: one dedicated optical channel (“lambda”) between two points, sold at a fixed rate.
- The provider runs dense wavelength-division multiplexing (DWDM) equipment that carries many such channels over the same fiber.
- Handoffs are usually Ethernet (10GE, 100GE, 400GE) or an optical transport format such as OTN.
- Latency is set mainly by route length, and stays steady because there is no routing or queuing in the provider’s path.
- Protection options and route diversity vary widely, so ask how each path runs.
What problem it solves
Organizations that move large volumes of data between fixed locations, such as two data centers replicating storage, a data center and a cloud on-ramp, or a media company moving video, outgrow shared and lower-speed services. Buying more Ethernet circuits gets expensive at high speeds, and routed services add variability. Dark fiber gives full control, but it requires owning and operating optical equipment, and spare fiber is not available on every route.
A wavelength fills that gap. You get dedicated, high-capacity bandwidth with predictable latency, without running an optical network yourself. Because it is a managed service, it can usually be ordered on routes where you could not get dark fiber, including long-haul routes between cities.
How it works
The optical layer. Providers use DWDM systems to carry many separate wavelengths of light over a single fiber pair. Each wavelength is an independent channel. Your service is assigned one channel end to end, with equipment at each site that converts your signal onto it and back.
The handoff. At each end you receive a port, typically Ethernet at the purchased speed, or an optical transport interface such as OTU2 or OTU4 for customers whose equipment expects it. Many wavelength services are transparent, passing your traffic through without the provider inspecting or altering it, though exact behavior varies by provider.
Protection and diversity. An unprotected wavelength follows one path. A protected wavelength has an alternate path or resource, and the provider’s equipment switches to it automatically if the primary fails. How separate that alternate is from the primary varies, so confirm physical route separation in the contract and route documentation. Some networks use reconfigurable optical add-drop multiplexers (ROADMs) to restore service over other routes after a cut. Alternatively, buyers order two wavelengths on separate routes and handle failover themselves.
Latency. Light travels through fiber at roughly 200 kilometers per millisecond, so latency follows the physical route rather than the straight-line distance. Providers can often quote the route length or a measured latency, and some sell low-latency routes at a premium.
For reference designs and diversity patterns, see our Wavelength solution page.
When it matters for buyers
- Data center interconnect. Replicating storage, extending networks between sites or running active-active applications needs high, steady bandwidth.
- Connecting to colocation and cloud on-ramps. A wavelength from your data center to a carrier-neutral facility can carry traffic to many cloud and network partners from one point.
- Capacity jumps. When you need 10 Gbps or more between two points, a wavelength is often cheaper per unit of bandwidth than multiple lower-speed circuits.
- Latency-sensitive work. Trading, real-time media and synchronous replication depend on known, stable delay.
- Comparing with dark fiber. If you need a lot of capacity on one route for many years, compare the long-term cost against leasing fiber and lighting it yourself.
Questions to ask vendors
- What is the exact route, its length, and the expected or measured latency?
- Is the service protected, and if so, how separate are the two paths and how fast is the switch-over?
- What handoff types and speeds are available, and is the service transparent to all of our traffic?
- What availability, repair-time and latency commitments are in the SLA?
- Is the route on your own fiber, or does any segment rely on another carrier?
- Does this path share conduit or building entry with our other connections?
- How quickly can we upgrade the speed, and does an upgrade require new equipment or a new installation?
How it differs from dark fiber
With dark fiber you lease the fiber strands themselves and install your own optical equipment, so you control how many channels run over it and at what speeds. A wavelength is one channel on the provider’s lit network, at a fixed speed, with the provider responsible for the optical equipment. Wavelengths are quicker to order and available on more routes; dark fiber gives more control and can cost less at very high capacity, but it requires optical skills. Dim fiber sits between the two.
Problems this helps with
- Replicating data between data centers needs more bandwidth than our circuits allow
- Latency between two sites varies when it should be fixed
- Need very high capacity without building and running our own optical network
