1.5 Compare and contrast transmission media and transceivers
Connector Types
📘CompTIA Network+ (N10-009)
What is an ST Connector?
The Straight Tip (ST) connector is a fiber-optic connector commonly used in older or legacy fiber networks. It is known for its round, bayonet-style locking mechanism and is most commonly found in multimode fiber installations.
Although ST connectors are not as common in new deployments today (because LC and SC connectors have become standard), you may still see ST connectors in many older network rooms, campus networks, or industrial environments.
For the exam, you must understand what the connector looks like, how it works, and where it is used.
Key Characteristics of an ST Connector
1. Connector Type: Fiber Optic
- Used for transmitting data through light, not electrical signals.
- Works with multimode fiber most of the time.
- Can support single-mode fiber, but this is less common.
2. Plug Type: Bayonet Twist Lock
- Uses a “twist-and-lock” bayonet mechanism.
- You insert the connector, twist it about ½ turn, and it locks into place.
- This locking system helps keep the connection secure, preventing accidental unplugging.
3. Physical Appearance
- Round body
- Long, metallic tip (2.5 mm ferrule)
- Usually has a spring-loaded mechanism to maintain stable contact.
4. Ferrule Size
- Uses a 2.5 mm ferrule, the same size as SC connectors.
- Larger ferrule than modern LC connectors (which use 1.25 mm ferrules).
How the ST Connector Works
- Light travels through the fiber core.
- The 2.5 mm ferrule holds the fiber in place.
- The bayonet-style twist ensures:
- Proper alignment between fibers
- Stable light transmission
- Minimal signal loss (low insertion loss)
Because ST connectors use a metallic and spring-loaded design, they are durable and were heavily used in environments where fiber cables are frequently moved or re-patched.
Where ST Connectors Are Used in IT Environments
While not as common today, you may still find ST connectors in:
1. Legacy campus networks
Older university or office buildings may still use ST fiber in network closets.
2. Fiber patch panels in older data centers
Some equipment racks installed years ago still have ST patch panels for multimode fiber.
3. Industrial or manufacturing networks
ST connectors were once preferred due to their durability and secure locking.
4. Older network backbone connections
Some organizations use ST fiber for their older backbone connections between network distribution switches.
Advantages of ST Connectors
✔ Durable and Reliable
The metallic body and spring mechanism ensure long-lasting performance.
✔ Secure Connection
Bayonet lock prevents accidental disconnection, useful in environments where cables are moved frequently.
✔ Good for Legacy Multimode Fiber
Was widely used for 62.5/125 µm multimode fiber.
Disadvantages of ST Connectors
✘ Bulky
Larger than modern connectors like LC.
✘ Not Common in New Installations
Most modern network equipment uses LC or SC ports.
✘ Slower to Connect
Twist-lock design requires more time than push-pull connectors like SC or LC.
✘ Higher Insertion Loss Than LC
LC connectors give more precise alignment, making them preferred today.
ST Connector vs Other Fiber Connectors (Exam Comparison)
| Connector | Ferrule Size | Mechanism | Typical Use | Notes |
|---|---|---|---|---|
| ST | 2.5 mm | Bayonet twist | Legacy multimode | Older networks |
| SC | 2.5 mm | Push/pull | Modern multimode/single-mode | Square shape |
| LC | 1.25 mm | Push/pull latch | Most modern fiber | Small form factor |
| FC | 2.5 mm | Screw-on | High-vibration environments | Rare today |
Knowing how ST compares to the others is often tested on Network+.
Common Exam Phrases You Must Recognize
You may see questions mentioning:
- “Bayonet-style fiber connector” → ST
- “Legacy multimode connector” → ST
- “Round fiber connector with twist-lock” → ST
- “2.5 mm ferrule connector used in older networks” → ST
Be prepared to identify ST by description and by purpose.
When You Would Use an ST Connector in Real IT Scenarios
Here are real IT-based examples (no unrelated analogies):
- Connecting an older fiber patch panel in a university to a network switch using ST-to-ST fiber patch cables.
- Replacing a broken ST fiber jumper in a legacy network closet.
- Migrating from ST-based multimode fiber to LC-based equipment, using a media adapter (ST to LC conversion).
These examples show realistic IT use cases that students may encounter.
Summary for Exam Success
- ST = Straight Tip = Fiber optic connector.
- Uses 2.5 mm ferrule.
- Known for bayonet-style twist-lock mechanism.
- Mostly used with multimode fiber.
- Common in legacy networks, older campus networks, industrial sites.
- Not common in new installations, replaced by SC and LC.
If you remember these key points, you will easily answer any ST-related question on the CompTIA Network+ exam.
