Compliance Is the First Gate, Not the Last
An RFoG receiver that is technically perfect but poorly documented does not pass a technical evaluation in Europe or North America. Establish what the unit must legally demonstrate before the optical design is discussed.
European Union
- CE marking, with the EMC assessment normally referenced to EN 50083-2, the EMC standard for cable network equipment.
- RoHS 2 — Directive 2011/65/EU, with a report that names the tested part numbers.
- WEEE obligations for electrical equipment placed on the market.
- REACH obligations for substances of very high concern.
North America
- FCC Part 15 emissions limits — Class A for a headend or hub, Class B where the unit sits in a residential or MDU cabinet.
- UL or ETL listing — a third-party (NRTL) safety listing is what a North American operator's safety review will ask for.
- SCTE reference standards, including the RFoG recommended practice (SCTE 174) that defines the wavelength plan most systems follow.
- California Proposition 65 labelling where applicable.
These are what the market requires. Ask what a supplier can actually hand over — a signed Declaration of Conformity, an EMC test report with part numbers, an NRTL certificate — not a compliance logo on a datasheet.
HENSURE holds CE marking and RoHS compliance; the Declaration of Conformity and the RoHS report are available on request. Certificate numbers and issuing bodies: 待用户补充.
What RFoG Actually Is
RFoG — RF over Glass — carries the RF signal, in both directions, on the same fibre that already carries PON data in an FTTH network. It works because each traffic type gets its own wavelength:
| Wavelength | Direction | Carries |
|---|---|---|
| 1490 nm | Downstream | PON / GPON / XGS-PON data |
| 1550 nm | Downstream | 1550 nm RF video overlay (linear TV) |
| 1310 nm | Upstream | PON data |
| 1610 nm | Upstream | RFoG return (cable modem upstream) |
The 1610 nm return makes this work: it sits far enough from the 1310 nm PON upstream that a simple WDM diplexer keeps them apart.
At the subscriber end sits a small R-ONU: it converts the downstream 1550 nm overlay to RF for the premises coax, and transmits the cable modem's upstream RF back at 1610 nm.
The Return Path Is the Hard Part
Downstream RFoG is straightforward. The return path is where deployments succeed or fail.
In a shared RFoG return, every subscriber's 1610 nm transmitter lands on the same fibre. When two transmitters run on closely spaced wavelengths, their optical mixing raises the noise floor — optical beat interference (OBI) — and return-path CNR falls. It appears as the plant fills, not in a single-subscriber test.
Practical mitigations:
- Specify wavelength-stabilised DFB return lasers, not the cheapest source.
- Ask for the OBI performance and the maximum number of R-ONUs per return-path port at which the quoted return CNR holds.
- Keep return-path combining ratios modest, and budget the return path separately from downstream.
- In a DOCSIS 3.1 / 4.0 build the upstream is the entire point — the return path is the last place to economise.
Reading the Datasheet: Insist on the Test Conditions
A quotation is a set of numbers; a number without conditions is not a specification. For each parameter below, ask for the channel count, OMI and optical input power at which it was measured:
- Downstream CNR / CSO / CTB — over how many channels, at what OMI, at what optical input power, and with what fibre in the path.
- Optical input power window — the minimum and maximum at which the specification holds, and the AGC range within it.
- Return-path CNR — at how many R-ONUs combined per port, and under what OBI conditions.
- RF output level — the level that is held, and whether AGC or MGC is used to hold it.
A single headline figure is the start of a conversation, not a specification.
Sizing the Optical Budget on an Existing PON
An RFoG link runs on the same fibre and splitters as its PON, so the budget is shared. Typical planning values:
| Element | Typical loss |
|---|---|
| Fibre attenuation at 1550 / 1610 nm | ≈ 0.20–0.25 dB/km |
| Connector pair | 0.3–0.5 dB |
| Fusion splice | ≈ 0.1 dB |
| 1:32 splitter | ≈ 15–17 dB |
| 1:64 splitter | ≈ 18–21 dB |
| WDM diplexer, per direction | typically under 1 dB |
The downstream 1550 nm overlay is the budget-sensitive direction: it must reach the last ONU in the split with enough power to hold its CNR. The upstream 1610 nm is easier on attenuation but harder on noise, for the OBI reasons above.
Where RFoG Fits — and Where It Does Not
RFoG is the right answer when:
- The operator must keep legacy set-top boxes and DOCSIS cable modems alive on a PON build.
- The site is an MDU or hospitality property where in-building re-cabling is not viable.
- The target is a node+0 / no-coax-in-the-drop architecture without field-powered nodes.
It is the wrong answer when:
- The roadmap is DOCSIS 4.0 with a high-split or full-duplex upstream that must run beyond the return-path bandwidth an RFoG link can carry — digital return or distributed access is the direction of travel.
- A 1.2 GHz HFC upgrade is planned and the downstream band has not been verified against what the RFoG ONU can pass.
Documentation, Warranty and RMA
EU and NA buyers judge a supplier on what happens after the purchase order. Ask for:
- A Declaration of Conformity and a RoHS test report, with part numbers matching the units ordered.
- A warranty term, and the RMA process: turnaround time, advance replacement, and who pays the freight.
- An optical and RF test report per unit or per batch.
HENSURE's MOQ structure, tiered pricing and warranty terms for RFoG receivers: 待用户补充.
Before You Request a Quote
- [ ] PON type and split ratio (GPON / XGS-PON, 1:32, 1:64 …)
- [ ] Downstream bandwidth required (862 MHz, 1 GHz, or 1.2 GHz)
- [ ] Number of R-ONUs to be combined per return-path port
- [ ] Return-path CNR target, and the conditions it must hold at
- [ ] Coexistence requirements with the 1310 nm PON upstream
- [ ] Compliance documents required (CE + EN 50083-2 EMC report, RoHS report, NRTL listing)
- [ ] Warranty and RMA terms
Bottom Line
RFoG is the least disruptive way to keep RF return alive on a PON already in the ground — provided the return path is designed rather than assumed. Settle the compliance file, the test conditions and the RMA terms before comparing prices; in EU and NA those decide more awards than unit price does.
Send us your PON topology and split ratios, and our engineering team will return an RFoG receiver recommendation with the return-path budget worked out.