In the field of optical fiber communication,
Fiber Optic Patch Cords are like "specialized data cables" connecting optical communication devices. Among them, SC/APC Fiber Optic Patch Cords feature excellent return loss performance and high system stability, making them indispensable in optical transmission scenarios sensitive to reflected light, such as cable television networks (CATV) and passive optical networks (PON).
During optical fiber transmission, when the optical signal reaches the connector endface, even with tight connection, a tiny amount of light will be reflected back. This reflected light mixes with the original signal, leading to signal distortion, reduced stability, and even damage to the light-emitting equipment.
(Difference in reflected light between PC/UPC and APC)
Currently, the mainstream is the 8-degree angle SC/APC Fiber Optic Patch Cord. Its principle and core function are basically the same as those of the 9-degree angle SC/APC Fiber Optic Patch Cord. However, the return loss of the 9-degree angle SC/APC Fiber Optic Patch Cord can reach above -65dB, which means the reflected light is weakened to an almost negligible level. It is specifically used in optical fiber systems requiring extremely low reflection and high signal stability.
(8-degree angle SC/APC is referred to as SC/APC8 hereinafter; 9-degree angle SC/APC is referred to as SC/APC9 hereinafter;)
II. Differences Between SC/APC8 and SC/APC9 Fiber Optic Patch Cords
Note: In principle, SC/APC8 and SC/APC9 Fiber Optic Patch Cords cannot be interoperably used for the following reasons:
- Poor physical contact: Mismatched angles prevent precise alignment of the fiber cores of the two connectors, leading to a sharp increase in loss (which may soar from 0.2dB to more than 1dB).
- Risk of endface damage: Mating with mismatched angles causes uneven contact pressure on the ceramic ferrule endface, resulting in scratches and permanent damage to the ceramic endface.
- Performance degradation: Even short-term connection will lead to a significant drop in return loss, failing to meet the performance requirements of the system.
III. Technical Characteristics and Application Scenarios
SC/APC8 and SC/APC9 Fiber Optic Patch Cords have the characteristics of extreme return loss, strong anti-interference ability, and stable performance, making them irreplaceable in fields with high requirements for signal stability:
1. Connection with Japanese-style Traditional Equipment
For connecting equipment in regions where SC/APC9 is the standard, such as traditional optical transmission equipment and local access network equipment (including OLT and optical repeaters) from manufacturers like Japan's NTT, the original products may have used the same type of interface. In this case, SC/APC9 Fiber Optic Patch Cords must be selected to match the equipment interface specifications and ensure normal signal transmission.
2. FTTx Fiber Access Networks
Whether it is Fiber to the Building (FTTB) or Fiber to the Home (FTTH), SC/APC Fiber Optic Patch Cords are widely used for connecting OLT (Optical Line Terminal) in operator computer rooms and ONU (Optical Network Unit/Optical Modem) at the user end due to their low reflection and easy plug-and-play features. For example, SC/APC8 Fiber Optic Patch Cords are standard in broadband access projects, which can avoid reflected light affecting the stability of broadband signal upload and download, supporting 1000M and above high-speed network transmission.
3. Radio and Television (CATV) and Analog Signal Transmission Systems
In the front-end computer rooms for cable television (CATV) and satellite TV signal access, SC/APC Fiber Optic Patch Cords are used to connect signal transmitters, optical splitters, and amplifiers. Since analog signals are extremely sensitive to reflection interference, the low return loss characteristic of APC can effectively avoid snowflakes and ghosting in the picture. For example, in the provincial backbone transmission network of China Radio and Television, SC/APC8 Fiber Optic Patch Cords have fully replaced traditional PC Fiber Optic Patch Cords, ensuring the stable broadcasting of 4K high-definition channels.
4. High-Precision Optical Fiber Testing and Operation and Maintenance
In OTDR (Optical Time Domain Reflectometer) link loss testing, loss verification after optical fiber fusion, and communication link fault diagnosis, SC/APC Fiber Optic Patch Cords (8-degree or 9-degree, need to match the equipment) are core tools. For example, when testing optical fiber links, using SC/APC8 Fiber Optic Patch Cords can avoid test signals being interfered by reflected light, accurately locate optical cable breakpoints and abnormal loss points, and improve operation and maintenance efficiency.
5. Industrial Control and Special Communication
- Industrial scenarios: In optical fiber sensing systems (such as temperature and pressure sensors) in the petroleum and power industries, SC/APC Fiber Optic Patch Cords are used to connect sensors and controllers. The low reflection characteristic can avoid signal misjudgment caused by environmental interference. For example, the temperature monitoring system of oil pipelines in oilfields achieves accurate monitoring of ±0.1℃ through SC/APC Fiber Optic Patch Cords.
- Special communication: In short-distance optical communication links in military and aerospace fields, SC/APC Fiber Optic Patch Cords are used for signal transmission between equipment due to their vibration resistance and stable contact characteristics, which can withstand extreme temperatures (-40℃~85℃) and mechanical shocks.
IV. Summary
SC/APC8 and SC/APC9 Fiber Optic Patch Cords share the same core principle, achieving excellent return loss performance and strong anti-interference ability through APC angled technology, and are suitable for scenarios requiring high signal stability. The core differences between them lie in the angle and regional adaptation: SC/APC8 is the global mainstream, compatible with equipment in most regions; SC/APC9 is exclusive to equipment in specific scenarios. It should be noted that interoperability between the two is prohibited. Standard use can ensure the efficient and stable operation of the optical transmission system.
