Connectors, Adapters & Passive Hardware
SC, LC, ST, MPO/MTP connectors - polish types, reflectance, patch cords, pigtails, attenuators, and dust caps.
- Identify SC, LC, ST, and MPO/MTP connector types and their applications
- Explain UPC vs APC polish types and reflectance values
- Describe patch cords, pigtails, and attenuators
- Explain ferrule care, keying, and connector orientation
- State why dust caps are essential for fiber connector protection
Lesson 1
SC, LC, ST & MPO/MTP Connector Families
The Four Major Connector Types
Fiber optic connectors terminate the fiber and provide a repeatable, low-loss interface for connecting fiber segments. Four connector families dominate the industry, and you must know each one for the CFOT exam.
SC (Subscriber Connector) is a square, push-pull connector widely used in telecommunications and data networks. It has a 2.5 mm ferrule and a simple push-on, pull-off latching mechanism. SC connectors are available in simplex and duplex configurations.
LC (Lucent Connector) is a compact, latched connector with a 1.25 mm ferrule - half the size of SC. LC is the dominant connector in modern data centers due to its small footprint, which allows higher port density. LC uses a latch similar to an RJ-45 jack.
ST (Straight Tip) uses a bayonet-style twist-lock mechanism with a 2.5 mm ferrule. ST was one of the first widely deployed connectors and is still found in legacy installations and some industrial applications.
MPO/MTP (Multi-fiber Push On) connectors terminate 12 or 24 fibers simultaneously in a single ferrule. They are essential for high-density data center applications and parallel optics (40G, 100G, 400G). MTP is the brand name for a high-performance version of the MPO standard.
SC Connector
Ferrule: 2.5 mm
Latch: Push-pull
Use: Telecom, FTTH, enterprise
LC Connector
Ferrule: 1.25 mm
Latch: RJ-45 style tab
Use: Data centers, high-density
ST Connector
Ferrule: 2.5 mm
Latch: Bayonet twist-lock
Use: Legacy, industrial
MPO/MTP Connector
Fibers: 12 or 24
Latch: Push-pull with key
Use: Data center, parallel optics
Connector Keying
Connector keying is important because it ensures the connector can only be inserted in the correct orientation. Keying prevents cross-connecting transmit and receive fibers, which would cause link failure. MPO/MTP connectors have a physical key (raised tab) that must align with the adapter's keyway.
Know the four connector families: SC (2.5 mm, push-pull), LC (1.25 mm, latched), ST (2.5 mm, bayonet), and MPO/MTP (12/24 fibers). LC dominates modern data centers. Connector keying ensures correct orientation and prevents cross-connections.