Fiber internet delivers your connection over glass instead of copper, using light instead of radio frequencies. That single difference is why fiber can offer symmetric speeds (the same up as down) and why it's far less prone to noise than cable. This article covers the basics and the acronyms you'll run into.
How a fiber network is built (PON)
Most residential and small-business fiber is delivered over a Passive Optical Network (PON). There are three pieces to know:
- OLT (Optical Line Terminal): the equipment at the provider's facility.
- Optical splitter: a passive device (no power required) that splits one fiber to serve many premises, commonly 1:32 or 1:64.
- ONT (Optical Network Terminal): the box at your location that converts light to Ethernet. Sometimes called an ONU.
Because the splitter is passive, the fiber between the provider and your building has no powered equipment to fail or inject noise, which is a big part of why fiber is so reliable.
The common flavors
- GPON: the most widely deployed standard. About 2.5 Gbps downstream and 1.25 Gbps upstream, shared across everyone on the splitter.
- XGS-PON: the current upgrade path. Symmetric 10 Gbps down and up (shared). This is what most providers are moving to for multi-gig service.
- EPON / 10G-EPON: an Ethernet-based PON standard used by some providers (including many cable operators expanding into fiber). 10G-EPON offers 10 Gbps and can be symmetric.
"Shared" is worth understanding: the headline speed is divided among the premises on a splitter. In practice, providers engineer this so users rarely notice, and it's a very different situation from a congested cable node.
PON is mostly for homes and small business
An important point of context: PON (GPON, XGS-PON, EPON) is primarily a residential and small-business access technology. It's shared, best-effort, and priced for volume, which is exactly right for most homes and small offices.
Enterprise-grade connectivity works in a fundamentally different way. Services like DIA (Dedicated Internet Access), EPL (Ethernet Private Line), and MPLS are not shared PON services. They are:
- Dedicated, not shared with neighbors on a splitter, so the bandwidth you buy is the bandwidth you get.
- Symmetric and committed, with a guaranteed rate rather than a "up to" figure.
- SLA-backed, with contractual uptime, latency, and repair-time commitments.
- Purpose-built topologies: DIA is dedicated internet to one site; EPL is a point-to-point private circuit between two sites; MPLS is a managed any-to-any private WAN linking many sites.
So while a PON plan and an enterprise circuit might both "run over fiber," they are different products for different needs. If uptime guarantees, dedicated bandwidth, or private site-to-site connectivity matter, that's an enterprise service, not PON.
Why fiber beats coax for upload
Cable (DOCSIS) reserves only a small slice of spectrum for upload and shares an RF medium that picks up noise from every home on the node. Fiber has no such constraint: upstream and downstream get equal capacity, and light in glass doesn't suffer the ingress and interference that plague coax. That's why fiber providers can advertise symmetric plans (for example 1 Gbps up and down, or 5 Gbps symmetric) that cable simply can't match today.
Passive vs. active fiber
The PON described above is "passive." Enterprise services are often delivered as Active Ethernet instead, giving a dedicated, unshared fiber path straight back to the provider. It's more expensive but offers guaranteed, non-shared bandwidth, which is what underpins DIA, EPL, and similar services.
Llama Networks sells and supports fiber and coax services, from residential and small-business PON to enterprise DIA, EPL, and MPLS. If you're deciding between fiber tiers or comparing options for a location, contact sales[at]llamanetworks[dot]com and we'll help you choose.