For those of you using hreflang for international pages: Make sure any rel=canonical you specify matches one of the URLs you use for the hreflang pairs.
If the specified canonical URL is not a part of the hreflang pairs, then the hreflang markup will be ignored.
In this case, if you want to use the "?op=1" URLs as canonicals, then the hreflang URLs should refer to those URLs. Alternately, if you want to use just "/page", then the rel=canonical should refer to that too.
Finally, don't use a rel=canonical across languages/countries, only use it on a per-country/language basis (don't specify the "de" page as the canonical for the "en" version, otherwise we won't index the "en" version).
There's much more about using hreflang on homepages at http://googlewebmastercentral.blogspot.ch/2014/05/creating-right-homepage-for-your.html
& a lot of information in our help center at https://support.google.com/webmasters/answer/189077
Edit: Some people asked about ways to recognize these issues on their site -- you can do that by using the hreflang tool as described in http://googlewebmastercentral.blogspot.ch/2014/07/troubleshooting-hreflang-annotations-in.html