How prestigious are the meetings of the Optical Society of America (OSA)? Usually, and especially for the IEEE conferences, it is easy to know whether a conference is good or not. For example, top-tier, second-tier and third-tier conferences are known and agreed upon. 

For example, the IEEE ICC (1st tier) conference is better than IEEE Globecom (2nd tier). My question is, how to define the tiers for the OSA meetings and conferences. 

Is there anyone familiar with the OSA meetings and conferences who can shed the light on how to interpret the acceptance in an OSA conference? What tier does an OSA conference belong to? How to know it, etc....

Kindly note that I am not asking if the acceptance as a poster, or even a talk is prestigious. I am strictly interested in the classification of the meeting and conference.

I know that a poster acceptance is less than being accepted for a talk, and that it is merely for discussions and feedback on new or emerging research topics. However, I believe that a poster presentation in a top tier, is better than a poster presentation in a second tier, therefore, I am asking about the OSA meetings and conference classifications.

Thank you.
AFAIK for disciplines related to the Optical Society of America (which is a well-recognized organization), the most prestigious things are journals - either by it (for example, JOSA A, JOSA B, Optics Express) or not (e.g. general physics or general science journals). When it comes to conference, its importance is related only to speakers/participants (so there is no general rule).

In any case, a poster presentation is never prestigious, be it by OSA or not (usually almost everything gets accepted).

I would ask that not every field have well-defined tiers for conferences. For example in mine, there isn't. And if you care for prestige - if you can't tell the difference - the chances are people seeing you CV won't be able to tell the difference either.

Usually review of abstracts (especially if no feedback is given) is to decide which things are suitable for talks (the best), posters (almost all others), and which - neither (they make no sense, are on another topic, of very poor quality or are OK but there is limited space for posters for some reason).