Within a data center, optical links are typically short (tens to hundreds of meters, up to ~2 km) and high-bandwidth, connecting leaf-spine switches, server racks, and increasingly, AI accelerator pods. These links form the fabric of AI clusters, where dozens or hundreds of GPU/TPU units must exchange data in parallel with minimal bottlenecks. 

Figure 3. Network configuration example and physical layer parameters for data center (Image source: Optica Publishing Group)

MCF offers several compelling advantages in this context:

• Massive Bandwidth Density: By carrying multiple spatial channels within a single fiber cladding, Multi‑Core Fiber (MCF) dramatically increases bandwidth per cable and per connector. For example, a single 4‑core MCF can replace four parallel single‑mode fibers typically used in a 400 GbE breakout (4×100 Gb/s) or even an 800 GbE link (4×200 Gb/s), reducing reliance on bulky multi‑fiber ribbons. In a demonstration by OFS, a single 125 µm‑cladding 8‑core fiber successfully supported 8×100 Gb/s = 800 Gb/s transmission over 2 km — performance that otherwise requires eight discrete SMFs in a typical DR8 or PSM4 setup [6]. Thus, MCF offers much higher fiber density inside conduit and data center cable trays, significantly simplifying infrastructure deployment. As link counts scale into the hundreds or thousands, this reduction in cable bulk becomes critical. MCF enables more compact paths between data centers or through congested underground ducts. While even higher core‑count fibers (7‑core, 12‑core) could further boost capacity, most intra‑DC deployments find 4–8 cores per fiber to be the practical sweet spot [6].

​​

• Reduced Fiber Footprint and Easier Management: Fewer physical fibers are needed for a given aggregate capacity. This translates to fewer connectors, fewer patch cords, and fewer terminations to handle. For network operators, that means less bulk to manage and maintain. A simple example: replacing four LC patch cords with a single 4-core MCF cable yields a 75% reduction in fiber count (and similar reduction in space occupied) [4]. Over an entire facility with, say, 10,000 internal links, the fiber count reduction is enormous. As Table 1 showed, the MCF approach consolidates multiple light paths in one strand, which simplifies cable routing and could reduce the size of cable bundles by a factor equal to the core count. Technicians would no longer need to install and label as many individual fibers; instead, they manage one fiber carrying multiple channels. This can improve reliability as well – fewer physical connections mean fewer points of failure. (It’s worth noting that losing one MCF could drop multiple channels at once, but appropriate redundancy in network topology can compensate for that, similar to how fiber trunk failures are handled today.) Industry experts expect the first applications of SDM fibers to be in data centers precisely because of these manageability and density benefits, where “simply increasing the number of optical fiber links may be too costly and unmanageable” and SDM provides a more scalable alternative [6, 8].

​​

• Cost Efficiency – Scaling Bandwidth without Linear Cost Increase: In the long run, MCF has the potential to lower the cost per Gb/s of transmission. Initially, MCF fibers and connectors are more expensive than commodity SMF, due to more complex fabrication and lower production volume. However, there are intrinsic cost advantages when scaling to many cores. The fiber raw material (glass preform) cost per core drops substantially – a 4-core MCF, for example, uses only marginally more glass than an SMF, so material cost per fiber core is ~25% of a single fiber’s. The main added cost is in processing (making the preform with multiple cores, ensuring quality, etc.). Fujikura notes that by increasing preform size (to draw longer fiber from one multi-core preform) and optimizing manufacturing, they can sharply reduce the processing cost per core. With ongoing R&D, volume production of standard-diameter MCF is becoming feasible – Fujikura recently drew a 600 km-long spool of 4-core fiber from one preform, a world record demonstrating manufacturing maturity [12]. From a system perspective, using MCF can also cut costs in other ways: fewer fibers to install (labor savings), fewer connectors and patch panels, and potentially consolidation of transceivers. For instance, rather than using four separate optical modules for four fibers, one could use a single module that interfaces with an MCF and carries four channels. This integration (one multi-channel module vs. four separate modules) could yield cost savings in packaging and power. Today’s transceivers are often limited by faceplate density – MCF allows fewer physical ports to achieve the same throughput, delaying or avoiding costly upgrades to new form- factors or more expensive higher-speed optics. In summary, while MCF components carry a premium initially, the cost per Gb/s is expected to drop below that of deploying equivalent parallel fibers, as the technology scales and standardizes.

​​

• Power Efficiency and “Green” Scaling: Multi-core fibers can also confer power savings in certain scenarios. This is somewhat subtle for short links (since no optical amplification is used intra-data- center), but the consolidation of optics can reduce overhead power. If four channels go through one module instead of four, you eliminate redundant control circuitry, and potentially share components like lasers. For example, researchers have explored using one laser source feeding multiple modulators for different cores in externally modulated systems, or using a single multi-core driver IC. Similarly, by sharing TEC (thermoelectric cooling) devices across multiple cores within transceivers or repeaters, additional power savings can be achieved. Additionally, optical power requirements per core are lower to achieve a given total throughput when using parallel cores. In long-haul systems, this is dramatic – splitting power across cores avoids nonlinear Shannon-limit penalties in one core [7], thus improving bits per watt. In data centers, the nonlinearity isn’t a limiting factor, but there is still an advantage: multi-core fan-out devices have shown very low loss (on the order of 0.2–0.5 dB total for distributing signals to cores), so nearly all launched power reaches the receivers across the cores. If we replaced those cores with separate fibers and connectors, the total insertion loss could be higher (each fiber has connector loss, etc.), which might require higher laser output or more amplification. Moreover, an MCF link can sometimes allow streamlining the network topology – for instance, using one fiber to directly connect two multi-port devices (through a multi-core connector) where otherwise multiple parallel links and perhaps extra intermediate switches would be needed. This can reduce the active equipment and thus electrical power consumption. Finally, high-core-count fibers could enable new architectures like optical circuit switching fabrics that cut down on energy usage by dynamically reconfiguring lightpaths; having many cores in one fiber simplifies such fabric connectivity. The EXAT consortium specifically highlights energy savings with SDM as a benefit, expecting integrated MCF systems to yield space and power efficiencies in densely scaled networks [7].

​​

• High Bandwidth Scaling for AI and HPC: Modern AI training clusters (sometimes called “AI supercomputers”) require all-to-all high-bandwidth connectivity between accelerator nodes. This puts tremendous stress on the data center network, often necessitating multiple tiers of switches and enormous cable counts. MCF provides a way to scale these fabrics with minimal disruption to existing optics. A set of standard 100 Gb/s or 200 Gb/s optical lanes can be grouped into one fiber to create a multi-terabit link, without resorting to exotic new modulation or >400 Gb/s single-channel transceivers. For example, using 8-core fibers, it is conceivable to achieve 8×100 Gb/s = 800 Gb/s on a single fiber without any electrical multiplexing – something impossible on one SMF without either running 8 wavelengths (which would need expensive WDM lasers) or moving to a new 800G serial standard. In fact, a 1.6 Tb/s short-reach link was demonstrated using a 4-core MCF carrying four wavelengths (400 Gb/s per wavelength using 56 Gbaud PAM4) [6]. This showcases how MCF can facilitate terabit-scale connections by combining readily achievable per-channel rates. The business implication is clear: data center operators can meet scaling demands by adopting MCF links, leveraging existing Ethernet optics technology on multiple cores, rather than waiting for ultra- complex single-channel solutions. This is a parallelism approach to scaling, much like multi-core CPUs increased processing power in computing. Crucially, it’s done in the optical domain, where it is far more cost-effective and energy-efficient than aggregating channels electronically.

​​

• Direct Integration with Silicon Photonics: An often overlooked but significant advantage of MCF is how it meshes with emerging silicon photonic (SiPh) interfaces. Silicon photonics allows integration of many optical transmitters and receivers onto chips (or chiplets) that can be co-packaged with switches or mounted near CPUs/GPUs. These photonic chips naturally produce multiple optical lanes (arrays of modulators, waveguides, etc.). MCF is an ideal companion, as a single fiber can carry all those lanes at once. Instead of having, say, 8 separate fiber pigtails coming out of a co-packaged optics module (which poses a routing nightmare on a dense PCB), one could have just 1 or 2 MCFs carrying all the channels. In essence, MCF provides a high-density optical I/O that matches the high-density electrical I/O of advanced chips. Researchers have explicitly pointed out that linear- array MCF designs (e.g. a 2×4 core arrangement) can map directly to transceiver arrays on PICs (photonic integrated circuits) [6]. By using an MCF with cores laid out to mirror the spacing of on-chip lasers or photodiodes, one can couple the chip to the fiber with potentially simpler optics. This greatly simplifies packaging for next-generation transceivers and could enable pluggable or onboard modules where a single connector carries multiple high-speed channels. In a 2019 paper presented at OFC (Optical Fiber Communication Conference), the world’s largest conference for optical networking and communications, OFS scientists noted that MCF is well-suited for optical interconnects in data centers, where there is no need to address multicore amplification and that MCF systems can provide direct connectivity to silicon photonic (SiP) and InP chips for high-degree integration and high-density interconnects [6]. This means MCF can eliminate the intermediate fan-outs in some cases – the fiber itself plugs into a transceiver that has integrated multi-core coupling optics, making the entire link very streamlined. The payoff for the data center is not just more bandwidth, but also potentially simpler network assembly (fewer cables to plug) and lower loss interfaces, which circles back to power and cost benefits.

In summary, within data centers MCF enables much greater bandwidth per fiber run, yielding a leaner physical network that is easier to scale. It leverages parallelism in optics to meet demand growth in a way that’s compatible with existing infrastructure: MCF can be deployed using the same rack space and similar handling as normal fiber (especially with standard-diameter variants), but delivers multi-fiber capacity over a single strand. This is why many experts believe the first real-world adoptions of MCF will occur inside large data centers [3, 6, 14] – the environment is controlled (short, no amplifiers needed), and the immediate rewards (space, weight, and management savings) are significant for the operators.