Receiver optical subassembly with optical limiting element

1. A receiver optical subassembly comprising:

an enclosure within which a detector element is disposed;

a housing attached to the enclosure and defining a fiber receptacle configured so that when an optical fiber is received in the fiber receptacle, signals from the optical fiber are directed into the detector element; and

an optical limiting element permanently positioned between the detector element and the fiber receptacle, wherein the optical limiting element has a non-uniform optical attenuation property.

2. The receiver optical subassembly as recited in claim 1 , wherein the optical limiting element is one of: absorptive; or, refractive.

3. The receiver optical subassembly as recited in claim 1 , wherein the detector element comprises one of: an APD; or, a P-I-N photodiode.

4. The receiver optical subassembly as recited in claim 1 , wherein the optical limiting element has a property such that when power of the optical signal entering the optical limiting element falls within a predetermined range, power of the optical signal leaving the optical limiting element remains at or below a predetermined limit, wherein the predetermined limit is one of an optical overload limit; or, a damage threshold.

5. The receiver optical subassembly as recited in claim 1 , wherein the enclosure comprises a TO-can.

6. The receiver optical subassembly as recited in claim 5 , wherein the TO-can includes a window to which the optical limiting element is attached.

7. The receiver optical subassembly as recited in claim 1 , wherein the optical limiting element is incorporated into a physical contact element positioned adjacent to the fiber receptacle.

8. The receiver optical subassembly as recited in claim 1 , further comprising a physical contact element to which the optical limiting element is bonded, the physical contact element being interposed between the fiber receptacle and the detector element.

9. The receiver optical subassembly as recited in claim 1 , wherein the optical limiting element is positioned on the detector element.

10. The receiver optical subassembly as recited in claim 1 , wherein a transmissivity of the optical limiting element is substantially linear in a first range of input optical powers, and substantially non-linear in a second range of input optical powers.

11. The receiver optical subassembly as recited in claim 1 , further comprising a lens interposed between the fiber receptacle and the detector element.

12. The receive optical subassembly as recited in claim 1 , wherein the property of the optical limiting element is such that the optical limiting element has a transmissivity that is substantially unity until the power of the optical signal entering the optical limiting element falls within one of the following ranges: about −6 dBm to about +3 dBm; or, about +3 dBm to about +10 dBm.

13. An optical transceiver module comprising:

a printed circuit board;

a transmitter optical subassembly connected to the printed circuit board;

a receiver optical subassembly connected to the printed circuit board, and comprising:

a detector element;

a fiber receptacle configured so that when an optical fiber is received therein signals from the optical fiber pass into the detector element; and

means for optically attenuating an optical signal;

a fiber contacting element positioned between the means for optically attenuating an optical signal and the fiber receptacle, the fiber contacting element configured to prevent an optical fiber received by the fiber receptacle from contacting the means for optically attenuating an optical signal, and

a housing that substantially encloses the printed circuit board, the transmitter optical subassembly, and the receiver optical subassembly.

14. The optical transceiver module as recited in claim 13 , wherein the means for optically attenuating an optical signal only attenuates received optical signals when a power of a received optical signal falls within a predetermined range.

15. The optical transceiver module as recited in claim 13 , wherein the means for optically attenuating an optical signal absorbs optical power from a received signal only if the optical power of the received signal exceeds a predetermined limit.

16. The optical transceiver module as recited in claim 13 , wherein the means for optically attenuating an optical signal begins limiting optical power of an optical signal exiting the fiber when the optical power of the optical signal falls within one of the following ranges: about −6 dBm to about +3 dBm; or, about +3 dBm to about +10 dBm.

17. The optical transceiver module as recited in claim 13 , wherein the means for optically attenuating an optical signal operates by one of the following mechanisms: absorption; or, refraction.

18. The optical transceiver module as recited in claim 15 , wherein the predetermined limit is one of: an optical overload limit; or, an optical damage threshold.

19. The optical transceiver module as recited in claim 13 , wherein the detector element comprises one of: an APD; or, a P-I-N photodiode.

20. The receive optical subassembly as recited in claim 1 , wherein the property of the optical limiting element is such that the optical limiting element has a transmissivity that is substantially unity until the power of the optical signal entering the optical limiting element reaches an input power threshold at which point the transmissivity of the optical limiting element is no longer substantially unity.

21. The optical transceiver module as recited in claim 13 , wherein the means for attenuating the optical signal provides at least two different levels of attenuation.

22. The optical transceiver module as recited in claim 21 , wherein the at least two different levels of attenuation are produced based on an optical power of the optical signal.

23. An optical subassembly comprising:

an enclosure within which a detector element is disposed;

a housing receiving the enclosure at a first end and defining a fiber receptacle at a second end; and

an optical limiting element permanently positioned between the detector element and the fiber receptacle, wherein the optical limiting element is configured to have at least two different optical attenuation levels.

24. An optical subassembly according to claim 23 , wherein the at least two different optical attenuation levels are defined by an input power threshold.

25. An optical subassembly according to claim 24 , wherein transmissivity through the optical limiting material is approximately 100% when the input power of the input optical signal is at a power level below the input power threshold.

26. An optical subassembly according to claim 25 , wherein the transmissivity through the optical limiting material is less than approximately 100% when the input power of the input optical signal is at a level above the input power threshold.

27. An optical subassembly according to claim 23 , wherein the optical limiting element has non-uniform optical attenuation properties.

28. A transceiver comprising an optical assembly according to claim 23 , the transceiver further comprising:

a transmitter optical subassembly configured to transmit optical signals.

29. The receiver optical subassembly as recited in claim 1 , further comprising a lens interposed between the fiber receptacle and the optical limiting element.

30. The optical subassembly as recited in claim 23 , wherein the optical limiting element includes glass doped with an absorber.

31. The optical subassembly as recited in claim 23 , wherein the optical limiting element is affixed to a window of the enclosure.

32. The optical subassembly as recited in claim 23 , wherein the optical limiting element is positioned within the enclosure.

33. The optical subassembly as recited in claim 32 , wherein the optical limiting element is affixed to a top surface of the detector element.