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06 Numbers and Powers

Fiber Patch Cord or Pigtail: Choose by Connection End

Card No. 06·20294 · Updated · Standard formula, shown below

Total link loss (dB) 1.18 dB
Loss per km (dB/km)
3.50 dB/km
Result
Total fiber length (m)
50 m
You entered
Number of connections
2
You entered
You enter
Total fiber length (m), Number of connections
You get
Total link loss (dB), Loss per km (dB/km)
Rounding
2 dp

Choose between a fiber patch cord and a pigtail based on how the connection ends: a patch cord has connectors on both ends, while a pigtail has a connector on only one end and bare fiber on the other. If you need to connect two devices or two patch panels directly, use a patch cord; if you are splicing fiber to a connector inside a panel or enclosure, use a pigtail.

Formula

The calculator estimates the total optical loss of a fiber link. The formula is:

Total Loss (dB) = (Fiber Length × Attenuation per Meter) + (Number of Connections × Loss per Connection)

Where:

  • Fiber Length (m) – the total length of the fiber in meters.
  • Attenuation per Meter (dB/m) – the signal loss per meter of fiber. For single-mode fiber at 1310 nm, typical attenuation is 0.35 dB/km, which equals 0.00035 dB/m. For multimode at 850 nm, it’s about 2.5 dB/km (0.0025 dB/m). The calculator uses 0.0035 dB/m (3.5 dB/km) as a conservative average for both types.
  • Number of Connections – the total number of mated connector pairs in the link. Each connection adds about 0.5 dB loss (typical for a good quality connector).

This is a simplified model. Real-world loss also includes splice loss, bending loss, and connector quality. Use the result as a planning estimate, not a guarantee.

Worked Example

Using the defaults from the calculator: 50 meters of fiber and 2 connections.

  1. Fiber loss: 50 m × 0.0035 dB/m = 0.175 dB
  2. Connection loss: 2 × 0.5 dB = 1.0 dB
  3. Total loss: 0.175 + 1.0 = 1.175 dB

The calculator shows 1.18 dB when rounded to two decimals. This is the expected insertion loss for a short link with two connector pairs.

Patch Cord vs. Pigtail: The Core Difference

The fundamental difference is in the termination. A patch cord (also called a jumper or patch cable) has a connector on both ends – for example, LC to LC, SC to SC, or LC to SC. It is used to connect two devices, two ports, or a device to a patch panel. A pigtail is a short length of fiber with a connector on one end and bare, unterminated fiber on the other. The bare end is spliced (fusion or mechanical) to a longer run of fiber, effectively adding a connector to that fiber.

When you see a fiber distribution panel, the ports on the front are typically pigtails. The fiber coming from outside is spliced to the pigtail’s bare end inside the panel, and the connector end plugs into an adapter on the front. To connect that panel to a switch, you use a patch cord.

How to Choose: Look at the Termination Points

Ask yourself: What am I connecting to what?

  • Device to device – use a patch cord with the correct connectors on both ends.
  • Device to patch panel – use a patch cord from the device to the panel’s front port.
  • Outside plant fiber to a panel – use a pigtail, splicing the bare end to the incoming fiber.
  • Fiber to a transceiver – use a patch cord with the same connector as the transceiver (usually LC).

If you are installing a new fiber run between two buildings, you will likely use pigtails at both ends (inside the panels) and patch cords to connect the panels to your equipment. If you are just connecting two switches in the same rack, a patch cord is sufficient.

Connector Types and Polarity

Connectors must match on both ends. Common types:

  • LC – small form-factor, widely used in data centers and enterprise networks.
  • SC – square, push-pull, common in telecom and CATV.
  • ST – bayonet-style, older, still found in industrial settings.
  • FC – screw-on, used in high-vibration environments.

Also check the polish: UPC (ultra-polished) and APC (angled-polish) are not compatible. APC connectors (usually green) have an 8° angle and are used in applications where return loss matters, like GPON. Mixing UPC and APC can damage the connector.

Polarity matters for duplex patch cords (two fibers). An A-to-B cord is standard; A-to-A is used for crossover. Always verify the polarity when ordering.

Common Mistakes and How to Avoid Them

  • Using a patch cord when you need a pigtail – you cannot splice a patch cord easily; the extra connector is useless.
  • Using a pigtail when you need a patch cord – a pigtail has no second connector, so it won’t plug into a device.
  • Mismatching connector types – LC on one end and SC on the other is fine for a patch cord, but for a pigtail you need the connector that matches the adapter in the panel.
  • Ignoring fiber type – single-mode (OS2) and multimode (OM3/OM4) have different core sizes. A patch cord for multimode will not work well with single-mode transceivers.
  • Forgetting the polarity – for duplex connections, A-to-B is standard; a reversed cord will not light up.

Cost and Installation Considerations

Pigtails are generally cheaper per unit than patch cords because they have only one connector. However, splicing a pigtail requires a fusion splicer (or mechanical splicing kit), which adds labor and equipment cost. Patch cords are plug-and-play – you just plug them in. For a small job with one or two connections, a patch cord may be more cost-effective. For a large installation with many fibers, pigtails plus splicing is standard practice.

Also consider the length: patch cords come in fixed lengths (1 m, 2 m, 5 m, etc.). Pigtails are typically 1-2 meters long, and you splice them to the main cable. If you need a custom length between two devices, a patch cord is easier to find than making your own.

Frequently Asked Questions

Can I use a patch cord as a pigtail?

Technically, you could cut a patch cord in half and use one half as a pigtail, but it’s not recommended. The cut end would need to be stripped and spliced, and the connector quality may not be suitable for splicing. It’s simpler and more reliable to buy a proper pigtail.

How do I know if I need single-mode or multimode?

Check your transceiver or the network equipment. Single-mode uses 9/125 µm fiber and is for long distances; multimode uses 50/125 µm or 62.5/125 µm and is for short distances (up to a few hundred meters). The connector color is a hint: yellow is single-mode, orange or aqua is multimode.

What does UPC vs APC mean?

UPC (Ultra Physical Contact) and APC (Angled Physical Contact) are polishing styles. APC has an 8° angle and is usually green. They are not compatible – connecting them can damage the ferrule. Use the same type throughout your link.

Can I mix LC and SC connectors?

Yes, if you use a hybrid patch cord with LC on one end and SC on the other. Just ensure the fiber type and polish match. For pigtails, the connector must match the adapter in the panel.

How much loss is acceptable?

For a typical link, total loss should be below 1-2 dB for short runs. The calculator gives an estimate; use an optical power meter to verify actual loss. If loss is too high, check for dirty connectors, bad splices, or excessive bending.

Do I need to clean fiber connectors?

Yes. Dust and oils on the connector end face cause significant loss. Use a fiber cleaning kit (dry or wet) before each connection. Never touch the end face with your fingers.

Related

Formula used
in t | Total fiber length (m) | m | 50 | 0 | 100000
in p | Number of connections | - | 2 | 0 | 1000
out loss | Total link loss (dB) | dB | t * 0.0035 + p * 0.5 | 2
out loss_per_km | Loss per km (dB/km) | dB/km | 0.0035 * 1000 | 2

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.

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