1. A compound optical combiner for combining multiple optical signals, comprising: a set of combiners, wherein the set of combiners includes at least one polarization combiner optically and physically connected to at least one non-polarization combiner, wherein the non-polarization combiner combines a first set of input signals while preserving a polarization of each input signal in the first set of signals, and wherein the polarization combiner combines a second set of input signals while converting the polarization of at least one input signal in the second set of signals, wherein the non-polarization combiner comprises: a first non-polarization combiner for combining a first input signal and a second input signals into a first combined signal; and a second non-polarization combiner for combining a third input signal and a fourth input signals into a second combined signal, and wherein the polarization combiner comprises: a polarization converter for converting the polarity of the second combined signal; and a combiner for combining the first input signal and the second combined signal to produce an output signal having a first component in a fundamental transverse magnetic (TM) mode and a second component in a fundamental transverse electric (TE) mode.