That's why I engage the engineering resources on their end to make sure the chosen candidate will support the use case. I have now performed an A/B comparison and the FiberStore gear is inferior. Excessive loss on the mux and optics.
Just for comparison sake, I should say that we've bought passive DWDM muxes and SFP+'s from FibreStore, and we've had good experiences. At the lower end of the market, production quality can definitely vary, which means significant variances in optical losses. When we ordered from FibreStore, we specified the Optical Loss values that we were able to accept. They tested the muxes before shipping, and selected the ones which fitted our requirements. Out of all the SFP's we bought, there were one or two DoA. FibreStore replaced this without issue. I think the important thing to remember (particularly when buying "cheap") is that you need to know what you're buying, and what the risks are. With this in mind, it's possible to save money and get a decent product with some careful specification and management of the purchasing process. If you're not too sure what you're after, then I'd suggest spending more money and buying from a supplier who's more set up to hand-hold you through the process. Simon