JNP-QSFP-100G-LR4: the full specification, and the other part numbers for the same optic
JNP-QSFP-100G-LR4 is a 100GBASE-LR4 QSFP28 transceiver: four wavelengths, one duplex single-mode pair, 10 kilometres. That part is straightforward. What is not straightforward is that Juniper has published four names that resolve to the same physical module, and three more that look almost identical and are genuinely different parts. People order across those boundaries constantly, and […]
Choosing 400G optics: SR, DR, FR and LR, and what each one costs you in fibre
Choosing 400G optics looks like a distance problem. You know how far the link has to go, you pick the part that reaches that far, and you order it. It is not a distance problem. It is a fibre problem wearing a distance problem’s clothes — because the four letters on the end of the […]
BiDi transceivers: one fibre, two wavelengths, and the pairing rule that catches everyone
BiDi transceivers do something that sounds like it should not work: they carry a full-duplex link over a single strand of fibre. One strand, both directions, at the same time. They are also the source of more confused ordering than any other part of the optics catalogue — because the word “BiDi” is used in […]
The real TCO of 400G: power, price and compatibility
The real 400G transceiver cost is not the price on the optic, and every 400G business case starts the same way. Someone divides the price of a 400G optic by the price of a 100G optic, sees a number that looks bad, and the conversation stops there. It is the wrong sum. Not because 400G […]
Juniper QFX5120 compatible optics: the full list
Choosing QFX5120 compatible optics is more interesting than it looks. The QFX5120 is the switch a lot of data centre leaf layers ended up standardising on, and two things decide what you can plug into one: which model you have, and — on the 25G models — which group of four ports you are plugging […]
Catalyst 9300 and 9500 compatible optics: what works, by model and module
The Nexus range gets the data-centre attention, but the switches that actually carry most UK enterprises are Catalyst 9300s in the wiring closet and Catalyst 9500s in the core. And the optics question on Catalyst is structurally different from Nexus: on most 9300s the switch itself has no optical ports at all. The question is […]
800G and 1.6T migration: what to check before you buy optics
800G is no longer a roadmap slide. The optics ship in volume, two form factors have settled into their ecosystems, and the IEEE standard behind the mainstream variants has been published since 2024. What has not settled is the buying process — because an 800G transceiver migration fails or succeeds on details that never mattered […]
SFP-10G-SR: the full specification and every part number
SFP-10G-SR is the most deployed 10G optic in the world. It is also the one most often ordered by the wrong name, populated into fibre that cannot carry it, and blamed for faults it did not cause. This is the reference page for it: what the standard actually specifies, how far it genuinely goes on […]
Your optics will go end-of-sale before your switch does
Most people track the end-of-life date on the switch. Almost nobody tracks it on the optic — and the optic usually runs out first. That is not a criticism of anyone. It is a scheduling reality that follows directly from how vendors manage product lifecycles, it is fully published, and once you have seen it […]
Nexus 9300 compatible optics: which transceiver works in which model
If you run Nexus 9300s, you have asked it. Choosing Nexus 9300 compatible optics should be a two-minute job, and it never is — because Cisco splits the answer across a datasheet, a hardware installation guide, an interfaces configuration guide and a compatibility matrix that only works in a browser. Nobody has all four open […]
