When choosing fiber optic cable, users will always be in a delimma: single-mode or multimode, which one should we choose? Although multimode is cheaper in price, many facts indicate that single-mode cabling is better for future-proof data center cabling.
Price is always the first factor that customers will take into consideration when purchasing products. Generally, the SMF itself is cheaper than MMF fiber ($1.10/meter vs. $3.70/meter for 24-strand OS2 vs. OM3 in FS.COM, and if you use SMF with LC interface and MMF with MTP interface for 40/100G, the price difference between SMF and MMF will be much great, 1M LC fiber cable vs. OM3 MTP fiber cable is $2.8 vs. $38 ), but the optics we should use with SMF vs. MMF are usually a bit more expensive. Take FS.COM as an example, SMF SFP vs. MMF SFP is $7 vs. $6, SMF vs. MMF SFP+ is $34 vs. $16, and with the increase of data rates, the price gap between SMF and MMF optics will be widen. We can get more detailed information from the table below.
From the price comparison between SMF and MMF cabling. You did save an amount of money to install MMF cabling, but you should consider the data rates that the MMF can support. In fact, in most cases, currently deployed MMF cabling is unable to support higher speeds over the same distance as lower-speed signals as shown in the table below since its cabling support for higher bit rates is limited by its large core size. As data traffic grows and interconnectivity speeds increase, the distance between connections must decrease, so the operators will be forced to constrain either the physical size of the data center or the connection speed between its nodes, which is unacceptable for most growing data centers. Besides, higher transmit rates will appear to meet more bandwidth requirements, IT managers will face with replacing an obsolete fiber plant, which will cause unexpected cabling costs.
Unlimited Bandwidth and Longer Distance: Unlike MMF, SMF cabling deployment support unlimited bandwidth, all but eliminating the capacity bottleneck. With unconstrained headroom, operators can safely settle into a network architecture with server interconnects that will scale with the data center. Many large data center operators, like Google and Microsoft have consciously adopted an SFM fiber cabling strategy in order to remove the network connectivity and speed constraints of a MMF plant.
Decreasing Cost: While using SMF cabling has historically been more expensive than using MMF, technologies advances have fundamentally changed the pricing structure. For example, price difference between 100G SMF and MMF optics is great, normally $2800 vs. $400, but there are newly designed 100G SMF optics, like QSFP28 PSM4 and QSFP28 CWDM4 as shown below, which is ideal for use for large data center. As the development of technology, the price for SMF cabling will continue decreasing.
Consistency: Single-mode cabling is used for external data center communication. By extending SMF into the data center, operators can leverage a consistent cable plant throughout the data center. Standardizing on a single cable plant will drive down sparing costs and reduce operational overhead.
Choosing SMF or MMF is forcing operators to choose between today and tomorrow. Although MMF provides tempting lower prices, it is not a long-term available solution. Operators should take the advantage of SMF’s limitless traffic carrying capacity and signal reach without incurring unnecessary cost overhead.