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Laser safety for integrators: what the module's class does and does not cover

A module datasheet says "Class 1". That statement is about the module. Your product needs its own classification, and the difference between the two is where builds fail certification.

Why 1535 nm exists at all

At 905 nm, light passes the cornea and is focused onto the retina, so the permissible exposure is low and the pulse energy a product may emit is small. Above roughly 1400 nm, water absorption in the cornea and lens removes the beam before the retina, so the permissible exposure is roughly two orders of magnitude higher. That is the entire technical reason a 23 km rangefinder can exist at 400 g — not better optics, a different hazard.

"Eye-safe" describes a wavelength band. It is not a certificate, and it does not transfer from the module to your product.

What changes when you integrate

Aperture and collimation. Accessible emission is measured at a defined distance from the aperture. Adding a window, a lens or a beam expander changes both the aperture and the divergence — and therefore the classification.
Repetition. A source at 10 Hz and the same source at 1 kHz are different exposure cases: pulse trains are evaluated per pulse, averaged, and in combination.
Multiple sources. Two emitters on one platform can add up at the eye even if each is individually below the limit.
The visible aiming channel. A 650 nm aiming laser is a separate hazard with a separate classification — 650 nm is focused by the eye. Do not fold it into the 1535 nm argument.

What to ask your module supplier for

The module's own classification statement, with the standard it was assessed against (IEC 60825-1 is the common one) and the revision year.
Pulse energy, pulse width and repetition rate — the three inputs to any exposure calculation.
Beam divergence and the aperture dimensions, so your integrator can redo the assessment with your optics in place.
Whether the classification was assessed on the bare module or on a reference configuration.

What the classification does not tell you

It does not tell you that your product is safe, that your export classification is settled, or that a customer's safety officer will accept it. Those are three separate conversations, and the third one is usually where a design-in stalls.

Need the module documents for an assessment? Ask per model: classification statement, pulse energy, width, repetition rate, divergence, aperture. Email tommy@erdimail.com Why the wavelengths differ

This page describes the integration problem, not a compliance conclusion. Classification of a finished product requires an assessment against the applicable standard by a competent person.