Patent ID: 8625989

Claim:
A multi-laser transmitter optical subassembly (TOSA) comprising: first and second lasers configured to generate first and second optical signals, respectively; a first polarization beam combiner (PBC); first and second collimating lenses positioned between the first and second lasers, respectively, and the first PBC; a first half waveplate positioned between the first laser and the first PBC; a focusing lens; third and fourth lasers configured to generate third and fourth optical signals, respectively; a second PBC positioned between the third and fourth lasers and the focusing lens; third and fourth collimating lenses positioned between the third and fourth lasers, respectively, and the second PBC; a second half waveplate positioned between the fourth collimating lens and the second PBC; a third PBC positioned between the first and second PBCs and the focusing lens; an isolator positioned between the first and second PBCs and the third PBC, the isolator comprising a polarizer garnet polarizer (PGP) isolator with a polarization axis that is about 45 degrees off of the horizontal or vertical plane; and a third half waveplate positioned between the isolator and the third PBC, wherein the first half waveplate is configured to rotate the polarization of the first optical signal, the first PBC is configured to combine the first and second optical signals and transmit the combined first and second optical signals toward the focusing lens, the second half waveplate is configured to rotate the polarization of the fourth optical signal, the second PBC is configured to combine the third and fourth optical signals and transmit the combined third and fourth optical signals, the third half waveplate is configured to rotate the polarization of the combined third and fourth optical signals, and the third PBC is configured to combine the combined first and second optical signals and the combined third and fourth optical signals and transmit the combined first, second, third, and fourth optical signals toward the focusing lens.