Choosing an OLT vendor: VSOL vs CDATA vs OPTILINK in practice

The honest answer is “it depends, and it’s usually whichever your TIP already runs.” The dishonest answer is “use the one with the highest PON count per chassis.”

We’ve installed and supported all three on BSNL SSAs. Here’s what we wish someone had told us before each one.

VSOL

The most common in Indian SSAs because the per-port cost is the lowest. The web console works on any browser. The CLI is simple. Default admin / admin usually works on the units we’ve received.

What we learned the hard way:

• The ONU table is paginated in a way that’s tedious to read at 200+ ONUs. Plan on building or buying a pane that flattens it.
• Signal levels are reported in tenths of dBm, not dBm. A reading of -275 means -27.5 dBm, not a dead ONU. We’ve seen technicians replace working drops because of this.
• Firmware updates require a reboot of the whole chassis. Schedule them.

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We picked VSOL because the price was right. Six months in, the cost is fine. The real cost is that we had to build a status pane on top of it.

CDATA

Slightly more expensive per port, slightly fancier CLI, slightly more vendor-doc availability. The web console is heavier and slower on a 4G hotspot. Default credentials vary by firmware revision — check the docs.

Worth it if:

• You’re building a single large pop and don’t want to babysit the OLT for firmware patches.
• You already have a CDATA-trained operator on the team — the CLI is similar enough across CDATA models that one skill carries.

Not worth it if:

• You’re replicating five small pops. The per-port cost adds up.
• Your upstream link is intermittent — the heavier console is painful over the BSNL proxy.

OPTILINK

Least common of the three. Strong specs on paper; field reality varies by model. We’ve seen one model where the ONU MAC table doesn’t expose the customer-side LAN MAC, which makes diagnostic correlation harder.

Use OPTILINK if:

• A BSNL SSA already standardised on it before you arrived. Replacing a vendor mid-rollout costs more than living with the quirks.
• You have a specific feature need (some models have better TR-069 surface).

Otherwise, keep it as a third-line option.

The actual decision

Run the simple test before you commit:

1. What can your on-call technician log into at 9 PM on Saturday? If the answer is “only VSOL,” pick VSOL.
2. What does your existing inventory look like? Mixing two vendors is fine. Mixing three is a training problem.
3. What does your pane support? If your operator app doesn’t speak the vendor, you’re paying twice — once for the OLT, once for a year of building integrations. FNW Flow ships with VSOL, CDATA, and OPTILINK; for an unknown vendor, the AI onboarder learns the login and ONU table itself, which gets you operational without waiting for a driver release.

The number on the spec sheet doesn’t matter as much as the answer to those three questions.

What we’d do today

For a greenfield small SSA: VSOL with a strong pane on top. The pane is where the operational lift comes from. The OLT is a commodity.

For a single large pop with one engineer babysitting: CDATA, accept the per-port premium.

For everything else: whatever your TIP is already running. The cost of vendor diversity is real, and rarely justified.