An SC/APC to SC/APC patch cord is a single-mode cable with an SC connector polished at 8 degrees at both ends, normally with green connector bodies. The angle sends reflected light out of the core, which PON, FTTH and CATV links depend on. It must mate only with APC ports, never SC/UPC. Radix Fibrotech makes these cords to order in Pune.
SC APC patch cord specification
An SC APC patch cord (SC/APC to SC/APC) has an angled-polish SC connector at each end, on single-mode fibre. This page covers the APC case in depth. The SC to SC patch cord page covers UPC and multimode options, and the UPC vs APC guide explains the end-face geometry. The SC connector guide describes the connector body.
| Feature | SC/APC to SC/APC cord | What to check |
|---|---|---|
| Fibre | 9/125 µm single-mode, G.652.D or bend-insensitive G.657.A1 or A2 | APC is a single-mode polish in practice; there is no common multimode SC/APC |
| End face | 8 degree angled polish at both ends | Both ends must match the ports they plug into |
| Ferrule | 2.5 mm, push-pull SC body | Fits SC/APC adapters only |
| Colour | Green connector body and boot by convention | Confirm the polish on the label or legend, not by colour alone |
| Return loss | 60 dB or better is the common industry figure for APC | Ask for the measured value in the report |
| Fibre count | Simplex or duplex | Simplex for PON and outlets |
| Jacket and diameter | LSZH, PVC or armoured; 2.0 or 3.0 mm | Thinner cords suit full frames |
| Length | Any length to order | Short for outlets, long for cross-connects |
Where SC/APC cords belong in a PON and CATV network
FTTH distribution frames
A passive optical network is a chain of mated joints: feeder, splitter, distribution frame, drop cable, outlet. In an SC/APC network every one of those joints is APC. A single SC/UPC joint in the chain reflects far more light than its neighbours, so it becomes the weak point of the link and the first place a technician looks when the budget fails. Cords inside the frame, from splitter outputs to the distribution side, are therefore SC/APC to SC/APC.
Wall outlets and ONT ports
The cord from the outlet to the ONT is short, often one to three metres, and handled by the installer. It sits in the worst conditions in the network: tight bends behind the outlet, repeated unplugging and dust. Specify G.657 bend-insensitive fibre here, keep dust caps in the pack, and label the polish on the cord so it is not swapped for a UPC cord during a service visit.
CATV and RF video over fibre
Cable television transport carries analogue and digital RF channels on a 1550 nm wavelength. Reflected light reaching the transmitter laser or an optical amplifier adds noise and distortion to those channels, which shows up as picture impairment. APC joints keep reflection low, and CATV transmitters, amplifiers and optical nodes commonly have SC/APC ports for this reason. Amplified transmitters put more optical power through the connector, so contamination does more damage there than on a low-power data link.
Testing APC links
Test sets, OTDR launch leads and power meter leads used on an APC network must be APC too. A UPC lead on an APC link creates a mismatch that the test then measures as if it were part of the plant.
Hybrid cords at the equipment
Some OLT optics and media converters have SC/UPC receptacles, so the cord from them into an APC frame is SC/UPC at one end and SC/APC at the other. That is a different part number from the all-APC cord on this page. Check the port label at each end.
Reading the green: colour convention and its limits
Green is the accepted colour for angled-polish connectors and adapters, and blue is the accepted colour for single-mode UPC. A green SC adapter in a frame or a green port on an ONT tells the installer to use an APC cord. The convention is useful but it has limits. Some sites colour cords by service or network instead of by polish, armoured and outdoor cords often have black outer sheaths, and a cord that has lost its boot colour in the field no longer shows its polish.
Treat colour as the first check, not the last. Ask for the polish to be printed on the cord label and in the jacket legend. For incoming goods, make the end-face inspection part of the receiving routine: a cord with an unmarked polish should be put aside and identified before it is used.
Simplex or duplex SC/APC cords
Simplex is the normal order for SC/APC. PON outlets, ONT ports, splitter ports and ODF positions each take one fibre, and a simplex cord leaves the neighbouring port free. A duplex SC/APC cord suits equipment that uses two fibres: two-fibre RF or video transport gear, optical nodes with separate forward and return fibres, and some DWDM and metro units.
Both connectors in a duplex clip should be APC, because duplex adapters and ports are made as APC or UPC units. If one fibre goes to an APC port and the other to a UPC port, order two simplex cords instead. Duplex cords are wired so transmit meets receive at the far end. If a duplex link does not light, flip the clip before suspecting the optics. In a frame, an unused duplex leg still needs a dust cap and a place to sit, which is why simplex is tidier where one fibre is wanted.
Mistakes with SC/APC cords
| Mistake | What happens | How to avoid it |
|---|---|---|
| Mating SC/APC with SC/UPC | The angled and domed faces leave an air gap. Loss is high, reflectance is poor and the faces can chip | Check polish at both ends and at the adapter; store APC and UPC cords in separate bins |
| Using a UPC adapter or UPC test lead on an APC link | The same mismatch, and the test result is false | Use green adapters and APC reference leads |
| Taking green to mean APC on every product | A cord coloured by service gets plugged into the wrong port | Confirm the polish from the label or legend |
| Tight bends at the outlet or ONT | Extra loss, worst at 1550 nm | Use bend-insensitive fibre and leave slack for a gentle loop |
| Plugging in without cleaning | Dirt raises loss and reflectance, and can pit the face | Inspect and clean both the cord and the port, then recap |
| Reusing a cord after a bad mate | A chipped face keeps causing loss on every later joint | Inspect after any suspected mismatch and replace a damaged cord |
Testing and reflectance on APC cords
Radix tests each SC/APC cord before dispatch. Insertion loss is measured at 1310 and 1550 nm, return loss on each connector, and end faces are inspected under magnification against IEC 61300-3-35 criteria. APC cords are measured against APC reference leads, since a UPC reference would add a mismatch of its own.
In service, a bad mate shows on an OTDR trace as a reflective event with high loss, usually larger than the clean joints around it. When a PON link fails its budget, look at reflective events first, then inspect the connectors at those positions. For a PON order, state the maximum insertion loss per connector and the minimum return loss in the quote, and count every joint in the loss budget. The fibre loss budget guide shows how.
What to send us for a quote
List each configuration on its own line, with:
- polish at each end, confirmed as APC to APC
- fibre standard: G.652.D, or G.657.A1 or A2 for tight routing
- simplex or duplex
- jacket, fire rating and outer diameter
- length and tolerance
- maximum insertion loss and minimum return loss, if set by the project
- label text, with polish and port references
- dust cap requirement and packing method
- test report format
- quantity for that line
Send the list through the request a quote page. If you need a different assembly from the standard cords, the custom fibre optic assemblies page explains how drawings are handled.
Questions buyers ask
What does a green SC connector mean?
Green marks an angled-polish APC connector, and green adapters in a frame mark APC ports. Colour is a convention, so confirm the polish from the label or the product legend when a site colours cords by service.
What happens if SC/APC meets SC/UPC?
The 8 degree face and the domed face do not touch squarely, so there is an air gap. Loss is high, reflectance is poor and the faces can chip. The link may light but fail its test, and the damaged cord should be replaced.
Why does CATV use APC connectors?
RF video channels on 1550 nm are sensitive to reflected light, which adds noise and distortion at the transmitter or amplifier. The angled face sends reflections out of the core, keeping them low. Amplified transmitters also make clean end faces more important.
How can I tell an SC/APC cord from an SC/UPC cord?
Check the colour first: green for APC and blue for single-mode UPC. Then read the label or jacket legend. If neither shows the polish, do not use the cord on an APC link until it has been identified.
What return loss should an SC/APC cord have?
60 dB or better is the widely used industry figure for APC, against 50 dB or better for UPC. Ask for the measured value in the report, and set a project limit in the quote if your specification has one.
Should SC/APC cords use bend-insensitive fibre?
Often yes, especially at wall outlets, ONTs and crowded frames where the cord is looped tightly. G.657.A1 or A2 fibre mates with G.652.D plant, so it can replace a standard cord without changing the link.