SN vs CS vs MDC: What to know about VSFF Fiber Patch Cords?

As data centers continue to increasing the number of servers, switches, and storage devices to support massive data growth and emerging high performance computing (HPC) applications such as artificial intelligence (AI), fiber density is increasing rapidly. Thus, Very Small Form Factor (VSFF) fiber optic patch cord have emerged to maximize space utilization in high density cabling, such as CS fiber patch cords, SN fiber patch cords, MDC cable, as well as SN-MT fiber patch cords and MMC cable. Let’s take a look at what is VSFF fiber patch cord?

 

VSFF Fiber Patch Cord, Designed for Higher Density

Fiber optic technicians are very familiar with duplex fiber optic patch cord, such as SC/ST/FC fiber patchcord, as well as the widely used LC fiber patchcord. Meanwhile, in high density data centers, MPO/MTP cable are also commonly used. MPO/MTP cable bundle multiple fibers together for high speed parallel optical cabling.

However, as data centers become more complex and increasingly dense, traditional duplex fiber optic patchcord are no longer sufficient to meet growing demands. VSFF fiber optic patch cords have emerged to address this challenge, offering significant space savings in highly dense infrastructure environments.

Several types of VSFF fiber patch cords have entered the market, including CS fiber patch cords, SN fiber patch cords, and MDC cable, as well as SN-MT fiber patch cords and MMC cable. Let’s take a closer look at different VSFF fiber patchcord types below.

CS Fiber Patch Cord: Small Size and High Performance

CS fiber optic patchcord offers 40% higher density than duplex LC fiber jumper. Like the LC fiber connector, CS connector utilizes a proven 1.25mm ferrule, but the spacing between the two ferrules of the CS connector is only 3.8 mm, compared to 6.25mm for the LC fiber connector. The smaller spacing gives the CS connector an overall size of 7.85mm x 5.3mm, compared to 13mm x 10.7mm for the LC. This means that using CS fiber patch cords in a 1U fiber patch panel allows for a higher fiber count.

Key Features of CS Fiber Optic Patch Cord:

• Push-pull tab for easy insertion and removal

• Available in UPC and APC polish types for both multimode and singlemode fiber

• Max. insertion loss of 0.15dB

• Supports 400G dual-WDM applications via a dual-CS configuration in QSFP-DD modules

 

CS fiber patch cords are primarily designed to connect QSFP-DD transceiver. Only one LC optical patch cord fits into a QSFP-DD transceiver, limiting LC optical patch cord to single wavelength division multiplexing (WDM) applications. Achieving 400Gbps transmission using duplex LC fiber patch cords requires eight wavelengths per fiber (with a transmission or reception rate of 50 Gbps per wavelength), which drives up transceiver costs.

By comparison, accommodating 2x CS fiber patch cords within a single QSFP-DD transceiver supports dual-WDM 400Gbps applications (2x200Gbps) using four wavelengths per fiber, thereby reducing transceiver costs and increasing switch port density.

 

SN Fiber Optic Patch Cord: Optimized for Hyperscale Interconnects

SN fiber optic patch cords, an upgrade to CS fiber patch cords, fully meet the density upgrade demands of modern data centers. Engineered for interconnection in hyperscale data centers, SN fiber connector adopts a 1.25 mm ferrule with a 3.1 mm vertical pitch and a 3.85mm width, delivering three times the port density of duplex LC.

Key Features of SN Fiber Optic Patch Cord:

• Fits 4xSN fiber patchcord per QSFP-DD transceiver

• Excellent for 4x100G breakout links from a single 400G port

• Eliminates the need for fan-out patchcord or cassettes module

• Uses a push-pull boot with the same 1.25mm ferrule

 

SN fiber patch cords are primarily used with QSFP-DD transceivers and are ideally suited for transitioning from 8fibers applications to duplex applications (such as 4x100G breakout deployments). SN fiber optic patch cords is easy insertion and removal with Push-pull boot.

 

MDC Cable: A More Competitive Option

Developed by US Conec, MDC cables are more compact than SN fiber patch cords. The connector of MDC cable also utilize 1.25 mm ferrule, with the fibers arranged vertically. However, MDC cable and SN fiber patchcord are incompatible. Please don’t try plugging one into the other’s transceiver interface or patch panel port.

Key Features of MDC Cable:

• 4x MDC cable fit into a single QSFP-DD transceiver

• Competes directly with SN in hyperscale data center deployments

• Allowing up to 432fibers in 1RU rack

 

Conclusion

VSFF fiber optic patch cords represent not only merely an improvement, but a fundamental shift in how modern data centers are designed and scaled. As network speeds push beyond 400G toward 800G and beyond, VSFF technology will play a pivotal role in building efficient, scalable, and future proof optical communication infrastructure.

Selecting VSFF fiber patch cords, such as CS fiber patch cords, SN fiber patch cords, or MDC cable, is crucial for data center upgrades. As a professional fiber optic patch cords manufacturer, UnitekFiber offers high quality VSFF optical patchcord. Please contact us at sales@unitekfiber.com if you need any supports.