SFP SC vs LC：What's the difference?

Introduction

Small Form-factor Pluggable (SFP) optical modules have become one of the pillars of modern telecommunication and data communication networks. These transceivers, compact in their build, provide versatile functions with different types of connectors, such as Subscriber Connector (SC) and Lucent Connector (LC). However, many often puzzle over deciding which connector to use in specific situations. Here, we delve into a comparative discussion between SFP SC and LC connectors, their characteristics, and their respective benefits in the communication industry.
 

The Basics

Before diving into specifics, let's get a basic understanding of these two connectors. Both SFP SC and LC are fiber optic connectors used to terminate the end of an optical fiber, facilitating fast and highly reliable communication.

The SFP SC connector, also known as the "standard connector," is a non-optical disconnect connector equipped with a 2.5mm zirconia ceramic ferrule. It is known for its locking mechanism that provides an excellent secure connection, preventing any unwanted disconnects.

On the other hand, the SFP LC connector, commonly referred to as the "Lucent connector," uses a 1.25mm ferrule. The LC connector is known for its high-density connections and compact size, making it ideal for use in datacoms and telecoms environments where space is at a premium.
 

Comparative Analysis

1. Size and Density

The most glaring difference between SFP SC and LC connectors lies in their dimensions. LC connectors are almost half the size of their SC counterparts. This compact size allows LC connectors to fit into more dense spaces, allowing twice the port density of SC connectors. Therefore, in situations where space and density are of primary concern, LC connectors offer a distinct advantage.

2. Connection Safety

SC connectors use a "push-pull" locking system that ensures a secure, stable connection once the connector is in place. This feature significantly reduces the risk of accidental disconnection, which is crucial in applications demanding constant, uninterrupted connection. Although LC connectors also feature a latch as a locking mechanism, the connection stability of SC connectors is generally considered superior.

3. Versatility 

LC connectors' small form factor and high-density features make them more versatile in a range of applications. They are most commonly used in single-mode systems due to their performance stability and high precision. They are used extensively in digital, television, and telephone systems due to their high performance. On the other hand, SC connectors,with their easy-handling characteristic, are quite popular in analog systems and have been widely utilized in CATV and long-range network applications.

4. Compatibility

LC connectors have better compatibility with equipment such as SFP and SFP+ transceivers due to their small size. However, SC connectors, despite their larger size, have maintained their relevance due to their secure locking mechanism and durability.

5. Cost

Usually, the cost of LC and SC connectors varies slightly, but generally, LC connectors are more expensive than SC connectors due to their compact design and higher precision.

What do SFP SC and SFP LC represent respectively?

What is SFP SC?

SFP SC, also known as Subscriber Connector, Square Connector, or Standard Connector, refers to a type of fiber optic connector used in communication and data communication applications. The SC word in SFP SC stands for the type of interface the SFP module employs; in this, case it's the SC connector.

In detail, the SC is a non-optical disconnect connector with a push-pull coupling mechanism and keyed, molded housing to avoid rotational sensitivity. It features a 2.5mm ferrule, usually made from zirconia ceramic, but can also be constructed from stainless alloy or plastic. 

One of the significant advantages of the SC connector is its secure locking mechanism. This characteristic ensures a stable, firm connection that significantly reduces the risk of accidental disconnections, a crucial feature in network applications that demand continuous, uninterrupted connections. This has made SC connectors widely popular in single-mode systems, Cable Television (CATV), and other analog systems where stable connections are paramount. The SC connectors provide precision, reliability, and stability in optical fiber connections.
 

What is the advantage of SFP SC?

SFP SC, the equivalent of Standard Connector or Subscriber Connector, has several distinct advantages in communications and data networking:

1. Secure connection: SC connectors have a push-pull design coupling mechanism known for its locking feature, which provides a highly secure and stable connection. This significantly reduces the risk of accidental disconnections in networks requiring consistent, uninterrupted connections.

2. Wide application: Due to their sturdy construction and reliable connection, SC connectors have found widespread application in Cable Television (CATV), wherein multimode and single-mode systems are common. They are also utilized in long-haul telecommunications networks and other analog systems.

3. High performance: SC connectors deliver high precision and excellent performance in optical fiber connections. The 2.5mm zirconia ceramic ferrule ensures a precise alignment of fibers, enabling efficient data communication with minimal signal loss.

4. Durability: SC connectors are popular for their durability, ensuring longevity even in demanding network environments. They can withstand both environmental and mechanical strains, ensuring a longer lifespan and a lower total cost of enterprise networking operations.

5. Easy handling: The SC connector's push-pull coupling design makes it easier to engage and disengage with minimal effort. This makes it simple to install, even for operators without specialized training.

6. Cost-effect: Compared to some of the other connectors such as the LC (Lucent Connector), the SC connectors are generally more affordable, making them a cost-effective solution for various applications within the communication industry.
 

What are the Disadvantages of a SFP SC?

While SFP SC connectors have many advantages, there are a few disadvantages that are worth mentioning:

1. Size: The primary limitation of an SC connector is its size. SC connectors have a 2.5mm ferrule, one of the more sizable ones among the SFPs. This means that SC connectors occupy more space and provide less port density compared to smaller connectors like LC. As a result, they might not be the optimal choice for extremely high-density applications.

2. Compatibility: The large size of the SC connector may limit its compatibility with some newer equipment, designed to accommodate smaller connectors. As technology continues to advance, devices are being designed to be more compact, and space for connectors such as SC, may be limited.

3. Cost: While they may be more affordable upfront compared to some other connectors, the lower port density of SC connectors might necessitate the purchase of additional equipment to accommodate all connections in high-density environments. This could potentially result in higher long-term costs.

Nevertheless, SC connectors remain a viable choice for a wide range of networking and telecommunications applications, with their strengths in secure, stable connections and high-performance capabilities.
 

What is SFP LC?

SFP SC, the equivalent of Standard Connector or Subscriber Connector, has several distinct advantages in communications and data networking:

1. Secure connection: SC connectors have a push-pull design coupling mechanism known for its locking feature, which provides a highly secure and stable connection. This significantly reduces the risk of accidental disconnections in networks requiring consistent, uninterrupted connections.

2. Wide application: Due to their sturdy construction and reliable connection, SC connectors have found widespread application in Cable Television (CATV), wherein multimode and single-mode systems are common. They are also utilized in long-haul telecommunications networks and other analog systems.

3. High performance: SC connectors deliver high precision and excellent performance in optical fiber connections. The 2.5mm zirconia ceramic ferrule ensures a precise alignment of fibers, enabling efficient data communication with minimal signal loss.

4. Durability: SC connectors are popular for their durability, ensuring longevity even in demanding network environments. They can withstand both environmental and mechanical strains, ensuring a longer lifespan and a lower total cost of enterprise networking operations.

5. Easy handling: The SC connector's push-pull coupling design makes it easier to engage and disengage with minimal effort. This makes it simple to install, even for operators without specialized training.

6. Cost-effect: Compared to some of the other connectors such as the LC (Lucent Connector), the SC connectors are generally more affordable, making them a cost-effective solution for various applications within the communication industry.

 

What is the advantage of SFP LC?

The SFP LC, otherwise known as the Lucent Connector, presents a variety of benefits within the realm of data communication and telecommunications:

1. High Density: LC connectors are small in size with their 1.25mm ferrule. This compactness allows for high port density, meaning they can accommodate more connections within a given space. This trait makes them ideal for use in high-density networking environments like data centers.

2. Superior Performance: LC connectors offer excellent performance, especially in Single Mode Fiber (SMF) applications. The compact design and high precision provide stable and efficient data communication with minimal signal loss.

3. Versatility: Due to their small form factor, LC connectors are compatible with a multitude of equipment including Gigabit Interface Converters (GBIC), SFP, and SFP+ transceivers. Their versatility allows them to be used in a wide range of applications including digital, television, and telephone systems.

4. Easy to Handle: The LC connectors employ a latch as a locking mechanism which is straightforward to operate, making the connection and disconnection process easier.

5. Reduces Cross Talk: LC connectors are designed with a flange that significantly reduces cross talk (signal interference between channels), which further enhances performance.

While LC connectors are usually more expensive than their SC counterparts, their benefits such as compactness, high-density connection ability, and versatile compatibility make them an attractive choice for various networking applications where space and performance are premium considerations. In summary, LC connectors offer excellent scalability and high performance, making them a popular choice in modern telecommunication and data communication networks.

 

What are the Disadvantages of a SFP LC?

Despite their numerous advantages, SFP LC (Lucent Connector) connectors also have certain disadvantages:

1. Cost: LC connectors are generally more expensive compared to other types of connectors such as SC (Standard Connector). The high precision and meticulous design that accommodate their small size and high port density often come at a premium price.

2. Handling Difficulty: While LC connectors are small and provide high-density connections, their small size might make them harder to handle, particularly in hurry or in dark conditions. The latch mechanism can be a bit delicate and require careful handling.

3. Fragility: The LC connector's small size can also make it prone to damage or breakage. Users need to handle them with proper care when plugging or unplugging to avoid damaging the connector.

4. Not Ideal for High Power Applications: LC connectors are generally not as well suited for high power applications compared to larger connector types.

However, these disadvantages are often outweighed by the LC connector's compact size, scalability, precise alignment, high performance, and compatibility with a lot of modern telecommunications and data networking equipment. As such, it remains a widely popular choice in space-constrained environments.

 

Precautions for purchasing SFP SC and SFP LC:

When purchasing either SFP SC or SFP LC modules, a number of precautions should be taken into consideration to ensure performance and cost-effectiveness:

1. Consider the Application: The decision between SFP SC and SFP LC should be guided by the specific application at hand. If space and high-density connections are crucial, an SFP LC might be the better choice. However, if a secure and robust connection is paramount, an SFP SC could be more suitable.

2. Vendor Reputation: Always purchase from trusted and reliable vendors who offer quality products. Purchasing from a reputable vendor reduces the risk of procuring substandard modules that may fail prematurely.

3. Compatibility: Ensure the module's compatibility with your network equipment. Not all SFP modules are universally compatible with all devices. It's crucial to confirm that the module will work seamlessly with your existing network devices.

4. Certification and Standards: Verify whether the modules meet the required industrial standards and certifications. Compliant modules have a performance guarantee and offer better interoperability with other equipment.

5. Check the Connector's Condition: Before proceeding with the purchase, inspect the condition of the connectors, especially the ferrules. Any scratches or damages might affect performance and signal quality.

6. Read Product Specifications: Make sure to thoroughly understand product specifications like data rate, transmission distance, wavelength, fiber type (single-mode or multi-mode), and others to ensure they align with your networking requirements.

7. Cost Analysis: Consider your budget constraints and the long-term costs. While SFP LC may be more expensive than SFP SC upfront, the increased port density and space saving could lead to cost savings in the long run. Similarly, while SC connectors may be cheaper, they might incur additional costs later if increased port density is required.

8. Warranty and Support: Choose modules that come with a warranty and look for vendors that provide good customer service and technical support, to assist should there be any trouble with the modules.

When these precautions are considered and followed, the risk of facing any damages and additional costs in the future can be greatly reduced. These precautions will ensure that the SFP modules you purchase will effectively meet your network's needs, while also providing good value for money.

 

SFP Transceivers and Their Role in Modern Communication Applications

SFP is an abbreviation for small form-factor pluggable transceiver, which is an interface module used for communication applications. This transceiver can receive and transmit data and is used in both copper and fiber optic cables. In simple terms, the transceiver is a hot-swappable device that plugs into a port of a network device. These transceivers can support different communication standards such as Gigabit Ethernet, SONET, and fiber channels. SFP transceivers can be interfaced with LC and SC connectors. This interfacing lends them the name SFP LC transceiver and SFP SC connector. The next section gives you a basic idea of these connector types.

 

A Few Important Fiber Optic Devices to Connect LC and SC Connectors

The choice of LC and SC connectors will entirely depend on your application requirements. However, the following are a few devices that you may need while using these connectors.

• Media Converters: These devices enable signal conversion, and are largely used in networks that use both copper and fiber optic cables. There are copper to fiber, fiber to copperand fiber to fiber media converters to choose from. Nowadays, these converters are equipped with SFP transceivers, and they support LC and SC connectors.

• Network Switches: They are the most important network hardware, which connects different devices in the network. There are different types of network switches to choose from. Industrial switches, PoE switches, hardened switches, and so on are a few popular ones. Today, it is quite easy to find network switches with LC and SC SFP transceivers.

• High Definition Transmitters and Receivers: High definition serial digital interface (HD-SDI) is a standard for digital video transmission lines. These enable the transfer of unencrypted and uncompressed video and audio signals. HD-SDI converters, HDMI video systems, and HD-CVI, HD-AHD, and HD-TVI installation kitsare examples of High Definition transmitters and receivers.

SC connectors: stick and click

SC connectors are considered highly suitable for applications that demand high-precision signals and are sensitive to return loss. The FTTX networks and video delivery over RF signals are a case in point.

The new SC connectors further simplify installation, maximize yield and offer guaranteed insertion loss and return loss performance equivalent to the factory-terminated connectors. However, SC has a large connector housing and a 2.5-mm ferrule, and that makes it less suitable for densely populated racks and panels.

This lack of compact design, a crucial factor in the connection real estate for building fiber-optic routing gear, brings us to SC’s younger and smaller cousin, LC, also known as Little Connector.

 

LC connectors: younger and smaller

Lucent Technologies, now part of Nokia, developed LC connectors in the early 2000s amid complaints that ST and SC connectors were too bulky and easy to dislodge from fiber connections. However, the initial market response to LC connectors was lackluster due to a high license fee.

Eventually, with the availability of LC-compatible transceivers and other active networking components, this smaller version of SC connectors began taking off in new fiber applications such as fiber to the home (FTTH). The smaller form factor, with a 1.25-mm ferrule, was also a huge benefit in high-connection-density environments like data centers and telecom switching centers.

LC is also a push-pull connector, but unlike SC’s locking tab, it employs a latch with a smaller ferrule, and that makes it hugely popular in data communications and other high-density patch applications .

The low-profile push-pull housing in SC connectors maximizes panel density, while the direct push-pull latch ensures efficient insertion and removal. Moreover, the LC connector’s ability to be grouped into a keyed arrangement and locking clip, like RJ45 connectors, has become a major factor in its popularity.

Some LC connectors claim to have no epoxy and no polish, and that makes these connectors faster than devices with typical epoxy terminations. Such LC connectors facilitate quick repairs and terminations in tight spaces and are now being used in high-data-rate systems like 1-Gbit/s to 10-Gbit/s Ethernet and fiber-to-the-desk (FTTD) applications.

Some other designs offer curing fixture and pre-assembly of LC connector ferrules prior to polishing, which improves throughput and eliminates accidental fiber breaks. The new designs also feature the simultaneous rotation of both ferrules to ensure that bare fibers are not being exposed at any time during polarity reversal.

 

Our Recommendation and a Simple Explanation

Let us get to the more controversial aspect: a simple recommendation. Many sites simply say to use either. If you have existing SC panels, for example, then it may make sense to get at least some SC gear. We are going to heavily recommend LC for a lower-density connection, and here is a picture as for why, just look at the size.

The LC connector fits into standard SFP+/ SFP28 form factors (SFP+ shown above.) Fiber with LC connectors can also be used in higher-end QSFP+ or QSFP28 and run 40GbE or 100GbE networking. There is a huge advantage to using a single connector that will fit into the optics that you are likely to find in switches, network cards, and motherboards. With SFP+ and SFP28 being so widely used, it makes a lot of sense to standardize as much as possible on that least common denominator of a connector. The fact that the connector is also used in higher-end 100GbE optics, as an example, just shows that it is quite useful.

Realistically, one can convert SC to LC and LC to SC without much trouble. One can also utilize cassettes such as this one to put multiple LC (or SC) links over a MTP higher-density cable. From a data performance perspective, SC and LC are very similar but SC is a higher mating cycle counter. For most of our readers, they are going to be unlikely to plug in these connectors 50 times per connector, let alone 500.

Still, since it is highly likely that our readers will have LC devices, standardizing on that for patch panels and other components can make a lot of sense.

 

Conclusion

Fiber optic communication is set to grow significantly in the years to come. It is making its presence felt in industries like defense, healthcare, railways, oil and gas, and so on. The choice of the right cables and cable connectors as well as fiber optic devices is important to ensure a precise connection. 

Current and future communication technologies require fast speed, high efficiency and security. All interconnected large complex databases must be able to receive and transmit data without external interference. Both SC and LC SFP transceivers are designed to achieve this transmission. You can choose whether LC SFP transceiver or SC SFP transceiver according to your needs.

Each SFP connector type, be it SC or LC, has its respective attributes and determinants to consider based on the application they are required for. The LC’s compact size and high precision make it suitable for high-density connections and single-mode systems. In contrast, the SC’s secure locking mechanism and stability make it valuable in applications requiring secure and constant connections. Therefore, the decision between SC and LC connectors should be carefully made considering the specific needs, space availability, and objectives of the communication industry. No connector can be universally declared as the ultimate choice; the best-fit choice always depends on the use case, application, and network requirements.