Are there real orthogonal polarization modes in pulsar radio emission?

The Orthogonal Polarization Modes (OPM) have been reported observationally and accepted widely by pulsar researchers. However, no acceptable theory can show the origin of the OPM, which becomes a mystery in pulsar research field. Here a possible way to solve this mystery is presented. We ask a question: Does there exist any real so-called OPM in pulsar radiation? It is proposed in this paper that the `observed OPM' in individual pulses could be the results of depolarization of pulsar radiation and the observational uncertainties originated from polarimeter in observation. A possible way to check this idea is suggested. If the idea is verified, the pulsar research would be influenced significantly in theory and in observation.