Choosing a 100G LR4 Module
100G LR4 modules serve longer single-mode 100G links than CWDM4 modules, using four wavelengths over a longer reach, and choosing one means choosing between reach, fibre and host requirements rather than between brand names. This article explains the LR4 idea, how it differs from CWDM4, and what to ask before ordering, and it states plainly that no LR4 product page with a listed specification exists on this site.
What LR4 is
LR4 is a 100G single-mode line that carries four lanes, each on its own wavelength in the 1310nm region, multiplexed onto a single fibre pair for a longer reach than the CWDM4 line. The four-lane structure is shared with CWDM4, and the difference lies in the wavelength plan and the reach: LR4 is designed for longer links, while CWDM4 is designed for links up to a shorter distance. The two lines are not interchangeable, and a module from one line does not substitute for the other even though both are 100G single-mode modules.
The reach difference is the practical point. A link that fits CWDM4 does not need LR4, and paying for LR4 reach on a short link buys nothing. A link beyond CWDM4 reach needs LR4 or another longer-reach family, and ordering CWDM4 for that link will fail on distance regardless of any other figure. The first selection question is therefore the link length, measured along the installed route, compared against the reach of each line.
LR4 against CWDM4
The comparison between LR4 and CWDM4 turns on three items: reach, loss budget and host requirements. Reach is the headline difference, but loss budget matters as much, because a link within the reach figure but with excessive connector or splice loss can still fall outside the design budget. Host requirements matter because the forward error correction and lane configuration expected by the host must match the module, and a mismatch there fails even when the optical figures fit.
Cost follows reach in the usual direction: longer-reach modules cost more than shorter-reach modules for the same rate, because the laser and receiver design is more demanding. That cost gradient is the reason to choose the shortest reach that covers the link with margin, rather than the longest reach available. Over-specifying reach wastes money on every link, and under-specifying reach fails the link entirely, so the correct choice is the shortest reach that covers the measured length with a sensible margin.
What to measure before ordering LR4
Before ordering an LR4 module, measure the link length along the installed route including patch cords, count the connectors and splices to estimate the loss budget, and identify the host platform and its forward error correction support. Those four items - length, loss, host and error correction - decide whether LR4 fits and which LR4 variant fits, and none of them can be inferred from the rate alone. An enquiry that includes all four can usually be answered without a second round of questions.
Where the link length is close to the boundary between CWDM4 and LR4, the margin decision matters. A link just beyond CWDM4 reach with a comfortable loss budget is a clear LR4 case, while a link just inside CWDM4 reach with a tight loss budget may still be safer on LR4. State the measured length and the loss estimate in the enquiry so the boundary case can be judged on numbers rather than on a rule of thumb.
No LR4 product page here - what that means
No LR4 module with a listed specification is published on this site, so no LR4 product page exists here and no LR4 distance, wavelength set or power figure is published from published standard documents. Standard figures describe a standard, not a supplier's module, and publishing them as product figures would mislead a buyer into ordering against figures that no specific module has been shown to meet. The guide page for LR4 on this site explains the line at concept level for the same reason this article does.
An LR4 requirement should therefore be sent as an enquiry naming the distance, the fibre type, the host platform and the loss budget, and the figures will be confirmed per model. That route is slower than reading a product page, but it is the only route that produces figures tied to a specific module, and it is the route this site uses for every line that lacks a listed specification.
Before you send the enquiry
A good enquiry for any topic in this article names the rate, the wavelength, the fibre type, the distance, the connector, the quantity and the application, plus the host platform when compatibility matters and any certification document needed by name. Each item removes a round of questions, and together they usually allow a quotation and a compatibility confirmation without further correspondence. An enquiry that names only a rate, or only a module-style name, will need at least one further round, because none of the other items can be inferred from the rate alone.
Environment and quantity also belong in the first message. Quantity affects the quotation and the delivery schedule, and environment matters because the listed temperature range for a module covers ordinary indoor conditions; links in unconditioned spaces, in roof voids or in outdoor enclosures fall outside that range and should be raised explicitly. Stating the environment when it is not an ordinary indoor data center or wiring closet lets the temperature grade be confirmed as part of the order rather than discovered as a failure in summer or winter.
Finally, check whether the line you need has a product page on this site or only a guide page. A product page carries a listed specification for a specific model, and an enquiry against it can confirm price, stock and compatibility for that model. A guide page explains the line and routes you to an enquiry, because no listed specification exists for that line here. Knowing which of the two you are reading prevents the most common buying mistake on this site, which is treating a guide figure, a title figure or a standard figure as if it were a specification for a specific module.
Enquiry checklist
Before sending an enquiry, note the model or the rate you need, the wavelength, the fibre type, the distance, the connector, the quantity and the application. State whether the module must be compatible with a named host platform, and name any certification document you need. Minimum order quantity and lead time are unavailable at company level and are confirmed per model in the enquiry. Quotations are confirmed per order.
Send an enquiry | Sales contact: Ms. Vicky Tian, Sales Manager, +86 19860146913 | Telephone: 86-0755-82552969 | Email: dsale@topsfp.com
Frequently asked questions
How do I get a quotation?
Send an enquiry naming the model, the rate, the wavelength, the distance and the quantity you need, plus the application. Quotations are confirmed per order, and specifications are confirmed per model before payment. This site does not list fixed selling figures, and no price is shown for any model.
What certification documents can you provide?
The company states ISO 9001, CE, FC, 3C and RoHS names. Certificates are available upon request. If a buyer needs a certificate for a specific model, name the model in the enquiry so the correct document can be checked. No certificate numbers are published on this site.
Do the specifications on one page apply to the whole range?
No. Specifications are shown per model and must not be read across the whole range. Where a value is not listed for a model, the page says to confirm per model rather than filling in a generic figure, and where the source pages disagree, the page flags the conflict instead of choosing one value as fact.
What are the minimum order quantity and lead time?
At company level both are unavailable on this site and are confirmed per model in the enquiry. A single-model note, where one exists, is marked as applying to that model only and must not be read as a company-wide term.