The relationship between single-mode and multimode optics has been completely turned around by the unprecedented volumes coming from FTTx. The figure below shows Ovum's tracking of total optical fiber communications laser volumes used in both telecom and datacom applications. Since 2010 single-mode volumes have exceeded multimode volumes by a good margin.
Even historically, the often-held perception that multimode volumes were an order of magnitude greater is not borne out by the data. In fact, the difference between multimode and single-mode for the prior decade (2000-2009) was only about 30%. This is similar to the amount by which single-mode now surpasses multimode.
In the datacom vertical, the 10:1 ratio is in fact true and remains so (though the hyper-scale data center operators are now leading a shift toward single-mode.) The spotlight on very high-end telecom, such as long-haul DWDM, also took awareness away from the much higher quantities of non-WDM telecom optics.
The sharp rise in single-mode volumes since 2010 is due to FTTx deployments, particularly in China. The conventional view of telecom being lower volume dates from an era when the access network was predominantly copper. Access volumes are much higher than data center optics volumes - at least for now. The datacom industry knows this well and hopes to leverage the cost reductions that FTTx has delivered.
In fact, the demanding economics of broadband access have pushed vendors to innovate with cost reductions such as laser chips designed to allow low-cost packaging. Cisco's recent proprietary 40G Ethernet format uses bidirectional transmission over the same fiber, a capability heavily used already in FTTx but not previously seen in datacom.