Plan a CATV RF-over-fiber network in one step. Enter how many optical receivers you need to feed and how far away the farthest one is. The planner picks the smallest QuestTel transmitter or EDFA that closes the link, sizes the PLC splitter, and shows the optical power and estimated carrier-to-noise ratio (CNR) at every receiver.
Updated October 7, 2026 · Equipment figures from QuestTel datasheets
P_rx = P_tx − L_split − (α × d) − (N_c × 0.5 dB) − (N_s × 0.1 dB)
The design works when P_rx is at least the receiver minimum plus your margin, no higher than the receiver maximum, and high enough to reach the CNR target.
For CNR, the planner starts from the point each QuestTel receiver is specified at: 45 dB at −10 dBm for the L-RF-MN-RX and 51 dB at −2 dBm for the L-RF-19R-RX. It moves the CNR 1 dB for every 1 dB of optical power and caps it at the transmitter's 51 dB rating. EDFA designs carry another 1 dB allowance for amplifier noise. Treat the figure as a planning estimate: channel loading and modulation depth move the real number, so confirm it with a meter at commissioning.
A campus needs cable TV in 32 buildings. The farthest building is 8 km of fiber from the headend, the line-up includes analog channels, and each building gets an L-RF-MN-RX mini receiver. There are 4 connector pairs and 6 fusion splices end to end, and the design keeps 2 dB of margin. This is the planner's default design.
| Budget line | Value |
|---|---|
| L-RF-32mW-TX output, 32 mW | +15.1 dBm |
| 1x32 PLC splitter, maximum insertion loss | −17.3 dB |
| Fiber: 8 km × 0.35 dB/km at 1310 nm | −2.8 dB |
| 4 connector pairs × 0.5 dB | −2.0 dB |
| 6 fusion splices × 0.1 dB | −0.6 dB |
| Power at each receiver | −7.6 dBm |
−7.6 dBm sits 4.4 dB above the receiver's −12 dBm minimum, clearing the 2 dB margin, and gives an estimated CNR of 47.4 dB against the 47 dB target for analog channels. The next size down, the 16 mW transmitter, delivers −10.7 dBm: below the −10 dBm the margin requires, with an estimated CNR of 44.3 dB. So the smallest transmitter that works is the L-RF-32mW-TX. With analog channels it serves these 32 buildings out to 9.0 km; with an all-digital QAM line-up the CNR target drops to 35 dB and the same transmitter reaches 14.7 km.
Maximum receivers per source by distance to the farthest receiver. The first figure is for a line-up with analog channels (47 dB CNR target); the second is for digital QAM only (35 dB target). Assumes L-RF-MN-RX receivers, datasheet-maximum splitter loss, 4 connector pairs, 6 splices and 2 dB margin. Counts are whole splitter sizes; “—” means the source cannot reach even one receiver at that distance.
| Source | 2 km | 5 km | 10 km | 20 km | 40 km |
|---|---|---|---|---|---|
| L-RF-2mW-TX (1310 nm, 2 mW) | 4 / 4 | 2 / 4 | 2 / 2 | 1 / 1 | — |
| L-RF-4mW-TX (1310 nm, 4 mW) | 4 / 8 | 4 / 8 | 4 / 4 | 2 / 2 | — |
| L-RF-8mW-TX (1310 nm, 8 mW) | 8 / 16 | 8 / 16 | 8 / 8 | 2 / 4 | 1 / 1 |
| L-RF-16mW-TX (1310 nm, 16 mW) | 16 / 32 | 16 / 32 | 16 / 16 | 4 / 8 | 1 / 2 |
| L-RF-32mW-TX (1310 nm, 32 mW) | 32 / 64 | 32 / 32 | 16 / 32 | 8 / 16 | 2 / 4 |
| L-RF-EDFA-14dBm (1550 nm, +14 dBm) | 32 / 32 | 32 / 32 | 16 / 32 | 16 / 16 | 4 / 8 |
| L-RF-EDFA-18dBm (1550 nm, +18 dBm) | 64 / 128 | 32 / 64 | 32 / 64 | 32 / 32 | 8 / 16 |
| L-RF-EDFA-24dBm (1550 nm, +24 dBm) | 128 / 256 | 128 / 256 | 128 / 256 | 64 / 128 | 32 / 64 |
EDFA rows above +17 dBm assume the first splitter sits at the headend, so no single fiber carries more than about +17 dBm (see 1310 nm or 1550 nm below).
| Model | Wavelength | Output (mW) | Output (dBm) |
|---|---|---|---|
| L-RF-2mW-TX | 1310 nm | 2 | +3.0 |
| L-RF-4mW-TX | 1310 nm | 4 | +6.0 |
| L-RF-8mW-TX | 1310 nm | 8 | +9.0 |
| L-RF-16mW-TX | 1310 nm | 16 | +12.0 |
| L-RF-32mW-TX | 1310 nm | 32 | +15.1 |
| L-RF-EDFA-14dBm | 1535–1565 nm | 25.1 | +14.0 |
| L-RF-EDFA-18dBm | 1535–1565 nm | 63.1 | +18.0 |
| L-RF-EDFA-24dBm | 1535–1565 nm | 251.2 | +24.0 |
Each doubling of transmitter power adds 3 dB. Doubling the split ratio costs about 3.4 dB on QuestTel PLC splitters, so each step up the transmitter range roughly doubles the receivers it can feed until fiber loss takes over.
| Split | Model | Typical loss | Maximum loss |
|---|---|---|---|
| 1x2 | L-1x2-F-PLC | 4.0 dB | 4.1 dB |
| 1x4 | L-1x4-F-PLC | 7.2 dB | 7.6 dB |
| 1x8 | L-1x8-F-PLC | 10.4 dB | 10.9 dB |
| 1x16 | L-1x16-F-PLC | 13.4 dB | 13.9 dB |
| 1x32 | L-1x32-F-PLC | 16.4 dB | 17.3 dB |
| 1x64 | L-1x64-F-PLC | 19.9 dB | 21.4 dB |
Values include the SC/APC connectors on the splitter and hold from 1260 to 1650 nm, so the same splitter works at 1310 nm and 1550 nm. Past 64 receivers the planner cascades two stages, for example a 1x4 feeding four 1x32s for 128 receivers. More on how splitters and couplers work: fiber optic couplers.
| Receiver | Optical input | CNR specification | Best for |
|---|---|---|---|
| L-RF-MN-RX mini | −12 to +3 dBm | ≥ 45 dB at −10 dBm | Buildings and customer premises; adjustable RF output |
| L-RF-19R-RX rack-mount | −9 to +2 dBm | ≥ 51 dB at −2 dBm | Headends, hubs and equipment rooms; ≥ 108 dBµV output, SNMP management |
To hold a 47 dB CNR for analog channels, keep each L-RF-MN-RX at about −8 dBm or above and each L-RF-19R-RX at about −6 dBm or above. Receivers close to the headend can get too much light; the planner flags them and sizes an in-line attenuator.
The FCC requires at least 43 dB carrier-to-noise for analog cable channels at the subscriber (47 CFR §76.605). Digital 256-QAM channels run reliably from about 31 dB. The planner adds 4 dB to each for the coax network after the optical receiver, so it targets 47 dB for line-ups with analog channels and 35 dB for all-digital line-ups. Going all-digital often lets one transmitter feed twice as many receivers. Channel plans: CATV QAM channel center frequencies; how QAM works: QAM constellation.
A directly modulated 1310 nm CATV transmitter is the simplest fiber link: no amplifier, near-zero chromatic dispersion at 1310 nm, and up to 32 mW (+15.1 dBm) of launch power. It suits campus, hotel, hospital, stadium and municipal networks out to roughly 10–20 km with up to a few dozen receivers.
At 1550 nm, an erbium-doped fiber amplifier (EDFA) goes further: fiber loss drops to about 0.22 dB/km and a 24 dBm EDFA delivers 251 mW, enough for hundreds of receivers. The EDFA needs a 1550 nm CATV transmitter driving it, at −5 to +10 dBm into the amplifier. Two cautions apply. Launch more than about +17 dBm into a single fiber and stimulated Brillouin scattering degrades the signal, so high-power designs split at the headend first. And analog signals at 1550 nm are sensitive to chromatic dispersion, so the transmitter driving the EDFA must be specified for 1550 nm CATV. Background on the two windows: fiber wavelengths and transmission windows.
It depends on distance and the channel line-up. At 5 km with QuestTel L-RF-MN-RX receivers, a 32 mW 1310 nm transmitter feeds 32 receivers, and a 24 dBm 1550 nm EDFA feeds 128 receivers with analog channels or 256 with digital QAM only. The table above covers 2 to 40 km.
Power inside the receiver's input window, with margin above the minimum: −12 to +3 dBm for the L-RF-MN-RX and −9 to +2 dBm for the L-RF-19R-RX. To hold a 47 dB CNR for analog channels, keep each L-RF-MN-RX at about −8 dBm or above and each L-RF-19R-RX at about −6 dBm or above.
PLC splitters come in powers of two. Twenty receivers need a 1x32 splitter, and its insertion loss is the same whether 20 or 32 ports are used, so the spare ports are free room to grow.
Too much light overloads the receiver and raises distortion. Fit an in-line SC/APC optical attenuator on that receiver. The planner flags receivers close to the headend that would exceed the maximum and sizes the attenuator.
Yes. The link is transparent to the RF it carries, so analog, QAM, ATSC and DVB-C channels from 45 MHz up to 862 or 1003 MHz travel together. All-digital line-ups need far less CNR, which often lets one transmitter feed twice as many receivers.
Maximum, for a design that must work on every port. Typical loss is what most ports measure; use it only to see how much headroom the finished network is likely to have.
<a href="https://questtel.com/wiki/catv-fiber-network-planner">CATV Fiber Network Planner</a>