Wavelength division multiplexing

1. A system comprising:

a first light source configured to generate a first beam of light at a first wavelength;

a second light source configured to generate a second beam of light at a second wavelength;

a third light source configured to generate a third beam of light at a third wavelength;

a fourth light source configured to generate a fourth beam of light at a fourth wavelength;

a thin-film filter configured to receive the first beam and the fourth beam and configured to combine the first beam and the fourth beam into a fifth beam of light that includes the first beam at the first wavelength and the fourth beam at the fourth wavelength;

a first polarization beam splitter (PBS) configured to receive the second beam and the fifth beam and configured to combine the second beam and the fifth beam into a sixth beam of light that includes the first beam at the first wavelength, the second beam at the second wavelength, and the fourth beam at the fourth wavelength;

a wave plate configured to receive the sixth beam and configured to rotate a polarization orientation of the sixth beam; and

a second PBS configured to receive the third beam and the sixth beam following rotation of the polarization orientation of the sixth beam and configured to combine the third beam comprising a single beam and the sixth beam comprising a combined beam into a seventh beam of light that includes the first beam at the first wavelength, the second beam at the second wavelength, the third beam at the third wavelength, and the fourth beam at the fourth wavelength, and the sixth beam including at least a first plurality of the first, second, third and fourth beams having a first polarization and at least one of the first, second, third and fourth beams different from the first plurality having a different polarization than the first plurality.

2. The system of claim 1 , wherein:

the first wavelength and the second wavelength differ by 20 nanometers (nm);

the second wavelength and the third wavelength differ by 20 nm;

the third wavelength and the fourth wavelength differ by 20 nm;

the first wavelength and the third wavelength differ by 40 nm; and

the first wavelength and the fourth wavelength differ by 60 nm.

3. The system of claim 1 , wherein:

the first wavelength is at least substantially equal to 1270 nanometers (nm);

the second wavelength is at least substantially equal to 1290 nm;

the third wavelength is at least substantially equal to 1310 nm; and

the fourth wavelength is at least substantially equal to 1330 nm.

4. The system of claim 1 , wherein the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength are spaced according to a course wavelength division multiplexing (CWDM) standard.

5. The system of claim 1 , wherein:

the first beam and the fourth beam have a first polarization orientation; and

the second beam and the third beam have a second polarization orientation substantially perpendicular to the first polarization orientation.

6. The system of claim 5 , wherein:

the polarization orientation of the sixth beam includes the first polarization orientation and the second polarization orientation; and

rotation of the polarization orientation of the sixth beam by the wave plate includes rotation of the first polarization orientation and of the second polarization orientation by 45°.

7. The system of claim 5 , wherein the wave plate includes a half-wave plate configured to rotate the polarization orientation of the sixth beam by 45°.

8. The system of claim 7 , wherein the half-wave plate includes an axis aligned to 22.5°with respect to the first polarization orientation or with respect to the second polarization orientation.

9. The system of claim 1 , wherein the thin-film filter has a filter isolation between 40and 60 nanometers (nm).

10. A method comprising:

generating a first beam of light at a first wavelength;

generating a second beam of light at a second wavelength;

generating a third beam of light at a third wavelength;

generating a fourth beam of light at a fourth wavelength;

combining the first beam and the fourth beam into a fifth beam of light that includes the first beam at the first wavelength and the fourth beam at the fourth wavelength;

combining the second beam and the fifth beam into a sixth beam of light that includes the first beam at the first wavelength, the second beam at the second wavelength, and the fourth beam at the fourth wavelength;

rotating a polarization orientation of the sixth beam; and

combining the sixth beam comprising a combined beam, after rotating the polarization orientation of the sixth beam, and the third beam comprising a single beam into a seventh beam of light that includes the first beam at the first wavelength, the second beam at the second wavelength, the third beam at the third wavelength, and the fourth beam at the fourth wavelength, and the sixth beam including at least a first plurality of the first, second, third and fourth beams having a first polarization and at least one of the first, second, third and fourth beams different from the first plurality having a different polarization than the first plurality.

11. The method of claim 10 , wherein:

the first wavelength and the second wavelength differ by 20 nanometers (nm);

the second wavelength and the third wavelength differ by 20 nm;

the third wavelength and the fourth wavelength differ by 20 nm;

the first wavelength and the third wavelength differ by 40 nm; and

the first wavelength and the fourth wavelength differ by 60 nm.

12. The method of claim 10 , wherein:

the first wavelength is at least substantially equal to 1270 nanometers (nm);

the second wavelength is at least substantially equal to 1290 nm;

the third wavelength is at least substantially equal to 1310 nm; and

the fourth wavelength is at least substantially equal to 1330 nm.

13. The method of claim 10 , wherein the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength are spaced according to a course wavelength division multiplexing (CWDM) standard.

14. The method of claim 10 , wherein:

the first beam and the fourth beam have a first polarization orientation; and

the second beam and the third beam have a second polarization orientation substantially perpendicular to the first polarization orientation.

15. The method of claim 14 , wherein:

the polarization orientation of the sixth beam includes the first polarization orientation and the second polarization orientation; and

rotation of the polarization orientation of the sixth beam includes rotation of the first polarization orientation and of the second polarization orientation by 45°.

16. A method comprising:

modeling a first light source such that it is configured to generate a first beam of light at a first wavelength;

modeling a second light source such that it is configured to generate a second beam of light at a second wavelength;

modeling a third light source such that it is configured to generate a third beam of light at a third wavelength;

modeling a fourth light source such that it is configured to generate a fourth beam of light at a fourth wavelength;

modeling a thin-film filter such that it is configured to receive the first beam and the fourth beam and configured to combine the first beam and the fourth beam into a fifth beam of light that includes the first beam at the first wavelength and the fourth beam at the fourth wavelength;

modeling a first polarization beam splitter (PBS) such that it is configured to receive the second beam and the fifth beam and configured to combine the second beam and the fifth beam into a sixth beam of light that includes the first beam at the first wavelength, the second beam at the second wavelength, and the fourth beam at the fourth wavelength;

modeling a wave plate such that it is configured to receive the sixth beam and configured to rotate a polarization orientation of the sixth beam; and

modeling a second PBS such that it is configured to receive the third beam and the sixth beam following rotation of the polarization orientation of the sixth beam and configured to combine the third beam comprising a single beam and the sixth beam comprising a combined beam into a seventh beam of light that includes the first beam at the first wavelength, the second beam at the second wavelength, the third beam at the third wavelength, and the fourth beam at the fourth wavelength, and the sixth beam including at least a first plurality of the first, second, third and fourth beams having a first polarization and at least one of the first, second, third and fourth beams different from the first plurality having a different polarization than the first plurality.

17. The method of claim 16 , wherein:

the first wavelength and the second wavelength differ by 20 nanometers (nm);

the second wavelength and the third wavelength differ by 20 nm;

the third wavelength and the fourth wavelength differ by 20 nm;

the first wavelength and the third wavelength differ by 40 nm; and

the first wavelength and the fourth wavelength differ by 60 nm.

18. The method of claim 16 , wherein:

the first beam and the fourth beam have a first polarization orientation;

the second beam and the third beam have a second polarization orientation substantially perpendicular to the first polarization; and

modeling the first PBS and the second PBS configurations based on the first polarization orientation and the second polarization orientation.

19. The method of claim 16 , wherein modeling the wave plate includes modeling the wave plate as a half-wave plate configured to rotate the polarization orientation of the sixth beam by 45°.

20. The method of claim 16 , further comprising modeling the thin-film filter to have a filter isolation between 40 and 60 nanometers (nm).