SFP ports

SFP ("Small Form-factor Pluggable") ports are the most common way of connecting fibre modules to hardware. There is different variations of this, basically in increasing speed:

• SFP limited to around 1G
• SFP+ limited to around 10G. Typically SFP modules will work fine in an SFP+ port (limited to 1G)
• SFP28 same connector as SFTP+, but faster at 25G. Generally compatible with SFTP+ ports (limited to 10G)
• QSFP+ quad-SFP+, giving around 40G
• QSFP28 quad QFTP+ is 100G - can be split into 4x QSFP28 connections (25G each)

Vague compataiblity:

• SFP and SFP+ modules are compatible (slower module works in faster port)
• SFP28 and SFP+ are similar (slower module works in faster port)
• SFP28 and QSFP28 modules are different

Source: www.3coptics.com/News/28.html (archive.org link)

Single mode, multimode

• Single mode uses a single beam of light down a cable. Laser one end, reciver at the other. Allows operating at longer distance (e.g 5km), but more expensive. Typically uses yellow sheath
• Multi mode fibre (MMF) uses wider cable, allowing cheaper LED sources, with shorter ranges (probably under 1km). Typically uses orange or aqua sheath

Source (archive.org link)

Fibre cabling

Fibre cabling for networking has a few variations

• OM1 - thicker cable, uses LED optical source, orange sheath
• OM2 - narrow cable, uses LED optical source, orange sheath
• OM3 - same as OM2 but uses VCSEL (laser) as source, aqua sheath
• OM4 - same as OM3 but higher bandwidth
• OM5 - faster, for 100G cable, lime green sheath. Compatible with OM3 and OM4

Basically as the number increases, the possible bandwidth increases.

OM1 and OM2 are typically used up to 10G networking, and are typically used for multimode connections.

OM3 and OM4 are used with VCSEL laser sources, which are faster-switching laser so are typically used for longer-distance single-mode connection, and higher datarates (e.g 40G and 100G)

Source (archive.org link)

Connectors

There's a lot of different connectors (like 15), but in networking context it's typically either:

• LC connectors ("Lucent Connector", trademarked term) - by far most common now - small (~1.25mm) square connectors with a prominant retention clip (very vaguely like RJ45)
• SC connectors - slightly older, larger connector with 2.5mm ferrule and retained by indented shaping. Quite common larger connector, but increasingly replaced by smaller LC

There is, of course, further variations of connectors, e.g

• LC/PC is the most common, the PC part is "Physical Contact". This is a 0degree cut, and is most common (for OM1 and OM2), using a grey connector.
• LC/UPC "Ultra Phsyical Contact" - similar to PC but with a higher precision finish (more polished). Repeated reconnection can reduce the performance
• LC/APC is "Angled Physical Contact", cut at an 8 degrees prevent reflections back up the fiber. It uses a green connector

Source (archive.org link)

Summary

The RJ45 connector is pretty great.