SFP-10G-SR vs SFP-10G-LR: Which 10G Optic to Choose

Choose SFP-10G-SR for short reach over multimode fiber (up to 300m on OM3, 400m on OM4) inside a building or data center, and SFP-10G-LR for long reach over single-mode fiber (up to 10km) between buildings or across a campus. SR uses an 850nm multimode optic; LR uses a 1310nm single-mode optic. They are not interchangeable: SR will not link over single-mode fiber, and the two optics must match on both ends of the link. The deciding factor is your fiber plant and distance, not the switch. SR is the cheaper optic but multimode fiber is the more expensive cable for long runs; LR is the pricier optic but single-mode fiber is cheap to run far.

The short answer: match the optic to your fiber and distance

Both SFP-10G-SR and SFP-10G-LR are Cisco 10 Gigabit Ethernet transceivers in the SFP+ form factor. They are hot-swappable, use a duplex LC connector, and support Digital Optical Monitoring (DOM) so you can read transmit/receive power, temperature, and voltage from the CLI. What separates them is the optical technology, and that dictates the fiber you must run:

SFP-10G-SR (short reach) transmits at 850nm over multimode fiber (MMF). It is the default choice for in-rack, top-of-rack-to-aggregation, and intra-building links where distances are under a few hundred meters.

SFP-10G-LR (long reach) transmits at 1310nm over single-mode fiber (SMF) and reaches up to 10km. It is the choice for building-to-building, campus backbone, and any run too long for multimode.

The most common procurement mistake is buying the optic that matches the budget rather than the fiber already in the ground. If your existing plant is orange or aqua multimode, you need SR. If it is yellow single-mode, you need LR. Both ends of every link must use the same optic type — an SR cannot talk to an LR.

Side-by-side spec comparison

The table below covers the specifications that actually drive a buying decision. Note that SR distance depends heavily on multimode grade: legacy OM1/OM2 fiber sharply limits reach, while OM3 and OM4 are what you want for any modern 10G multimode run.

Fiber type and patch cables: get this right or the link won't come up

The optic is only half the link. The fiber and patch cables must match the optic's wavelength and mode, or the port will simply not establish light.

For SFP-10G-SR, use multimode fiber and multimode LC-to-LC duplex patch cords. For new 10G runs, specify OM3 (aqua) or OM4 (aqua or violet) — these are laser-optimized for 850nm and give you the 300m and 400m reach respectively. Avoid OM1/OM2 (orange) for new builds; they cap 10G reach at roughly 33m and 82m and will bottleneck any future upgrade.

For SFP-10G-LR, use single-mode fiber (OS1/OS2, jacket typically yellow) and single-mode LC-to-LC duplex patch cords. Single-mode patch cords are not interchangeable with multimode — the core diameter differs (9 micron vs 50 micron), and mixing them causes high loss or a dead link.

A practical tip: when you order optics, order the matching patch cords at the same time and label both ends. Mismatched or dirty LC connectors are the single most common cause of a 10G link that flaps or never comes up. If you are speccing a switch refresh, our team can build the optics-and-fiber line items into the same BOM as the chassis. See Cisco Optics & Transceivers for the full SFP+/QSFP range, or compare the platforms in Catalyst 9200 vs 9300 vs 9500.

Cost: cheaper optic vs cheaper cable

There are two costs to weigh, and they pull in opposite directions.

The optic itself: SFP-10G-SR is the less expensive transceiver. SFP-10G-LR carries a premium because the 1310nm single-mode laser is more precise and the reach is far greater.

The cable plant: This is where the math flips for long runs. Multimode fiber is more expensive per meter and gets dramatically more expensive as distance grows, while single-mode fiber is cheap to pull over long distances. For a 10-meter intra-rack jump, multimode plus SR is the obvious low-cost answer. For a 600-meter campus link, single-mode plus LR is both the only option that works (SR tops out well short) and frequently the cheaper total once cable is included.

The rule of thumb: under ~300m, SR almost always wins on total cost. Beyond it, LR is the answer — usually because SR simply cannot reach, not just on price. Used and refurbished optics exist, but for production links in regulated environments insist on genuine Cisco or fully tested equivalents, since a cheap optic that fails DOM or trips a software compatibility check costs far more in downtime than it saves.

Cisco platform support and CLI verification

Both optics are supported across Cisco's mainstream 10G-capable platforms running IOS-XE and NX-OS, including Catalyst 9000 series switches with SFP+ uplinks, Nexus data center switches, ASR/ISR routers with SFP+ interfaces, and UCS Fabric Interconnects. Always confirm the exact optic is on the platform's supported transceiver matrix for your software release before deploying — Cisco enforces a compatibility check, and an unsupported or counterfeit optic can be rejected or report errors.

On IOS-XE, verify a seated optic with show interfaces transceiver for DOM readings (Tx/Rx power, temperature) and show inventory to confirm the part number the switch detects. On NX-OS, use show interface transceiver details. If Rx power reads very low or absent, suspect a dirty connector, a mismatched fiber type (multimode patch on an LR optic, or vice versa), or a broken strand — not the optic itself. For data center and campus core platforms, see Nexus 9300 vs 9500 to confirm which chassis fits your density and uplink needs, and browse Cisco switches for the matching hardware.

Quick decision guide

Use this to pick in seconds: