MULTIPORT OPTICAL AMPLIFIER WITH VCSEL PUMP ARRAY AND GAIN CONTROL
(19)AUSTRALIAN PATENT OFFICE(54) Title MULTIPORT OPTICAL AMPLIFIER WITH VCSEL PUMP ARRAY AND GAIN CONTROL (51)6 International Patent Classification(s) H04B 010/17 HOIS 003/102(21) Application No: 2003277960(22) Application Date: 2003.10.30(87) WIPONo: WO04/040810 (30) Priority Data (31) Number (32) Date 2002952347 2002.10.30(33) Country AU(43) Publication Date : 2004.05.25(43) Publication Journal Date : 2004.06.24(71)Applicant(s)EDITH COWAN UNIVERSITY(72)Inventor(s)ESHRAGHIAN, Kamran; ALAMEH, Kamal (H) Application NoAU2003277960 A1(19)AUSTRALIAN PATENT OFFICE(54) Title MULTIPORT OPTICAL AMPLIFIER WITH VCSEL PUMP ARRAY AND GAIN CONTROL (51)6 International Patent Classification(s) H04B 010/17 HOIS 003/102(21) Application No: 2003277960(22) Application Date: 2003.10.30(87) WIPONo: WO04/040810 (30) Priority Data (31) Number (32) Date 2002952347 2002.10.30(33) Country AU(43) Publication Date : 2004.05.25(43) Publication Journal Date : 2004.06.24(71)Applicant(s)EDITH COWAN UNIVERSITY(72)Inventor(s)ESHRAGHIAN, Kamran; ALAMEH, Kamal An optical amplifier (200) has input means (117) and pump bean generating means (101). Waveguide means (113), such as Erbium-doped fibres, receive the input signal and output amplified signals. The amplifier (200) may have more than 64 input/output ports, and the pump generating means (101) may comprise an array of vertical cavity surface emitting lasers. Gain may be controlled by monitoring input signal and pump powers, and adjusting the pump driving current profile accordingly. The Claims Defining the invention are as Follows : 1. An optical amplifier comprising: input means for receiving input optical signals; beam generating means for generating pump beams; and waveguide means for receiving the optical signals from the input means, and pump beams from the beam generating means, the waveguide means being arranged to absorb the received pump beams and operable to amplify the received optical signal using stimulated emission of radiation, the pump beams being used to drive the waveguide means to provide the stimulated emission; wherein the beam generating means is a vertical cavity surface emitting laser.
2. An optical amplifier according to claim 1, further comprising routing means for receiving the input optical signals from the input means, and pump beams from the beam generating means, and for routing the received input optical signals and the pump beams to the waveguide means.
3. An optical amplifier according to claim 2, wherein the routing means comprises a glass or sapphire substrate.
4. An optical amplifier according to claim 2 or 3, wherein the routing means includes collimating and focusing means.
5. An optical amplifier according to claim 4, wherein the collimating and focusing means comprise a microlens array.
6. An optical amplifier according to claim 4, wherein the collimating and focusing means comprise diffractive optical elements. <Desc/Clms Page number 17> 7. An optical amplifier according to any preceding claim, further comprising monitoring means for monitoring the power of the optical signals and the pump beams.
8. An optical amplifier according to claim 7, wherein the monitoring means is a two-dimensional photodetector array.
9. An optical amplifier according to claim 8, wherein the vertical cavity surface emitting laser is an integrated circuit, integrated with the photodetector array.
10. An optical amplifier according to any preceding claim, wherein the input means has a multi-port configuration.
11. An optical amplifier according to claim 10, wherein the input means comprises an array of optical fibres.
12. An optical amplifier according to any preceding claim, wherein the waveguide means has a multi-port configuration.
13. An optical amplifier according to claim 12, wherein the waveguide means comprises an array of optical fibres.
14. An optical amplifier according to claim 13, wherein the fibres in the array of optical fibres are either core-pumped or cladding-pumped.
15. An optical amplifier according to claim 13 or 14, wherein the array of optical fibres comprises erbium-doped alumino-silicate fibres, or praseodymium- doped fluoride fibres.
16. An optical amplifier according to any preceding claim, wherein the vertical cavity surface emitting laser operates in transverse single-mode.
17. An optical amplifier according to any one of claims 1 to 15, wherein the vertical cavity surface emitting laser operates in multi-mode. <Desc/Clms Page number 18> 18. An optical amplifier according to any preceding claim, wherein the vertical cavity surface emitting laser is arranged with an external cavity resonator.
19. An optical amplifier, according to any preceding claim, further comprising a first detecting means for detecting pump beam signals, and a processor to which pump beam monitoring signals are suppiied, from the first detecting means, in response to the detected pump signals, the processor being operable to generate control signals for controlling the pump beam generating means, in response to the pump beam monitoring signals.
20. An optical amplifier according to claim 19, wherein the first detecting means is a photodetector array integrated on a semiconductor chip.
21. An optical amplifier according to claim 19 or 20, further comprising a second detecting means for detecting the input signal beams, with input monitoring signals being supplied from the second detecting means to the processor in response to detected input signals, the processor being operable to generate control signals for controlling the beam generating means, in response to received input monitoring signals, and pump beam monitoring signals.
22. An optical amplifier according to claim 21, wherein the second detecting means is a photodetector array.
23. An optical amplifier comprising: an optical substrate having top and bottom faces and two side faces extending between the top and bottom faces so that the substrate has a square-shaped cross-section; an input fibre array and an output doped fibre array respectively coupled to the side faces in alignment with each other, the input fibre array supplying input beams; <Desc/Clms Page number 19> a vertical cavity surface emitting laser (VCSEL) array and a top photodetector array arranged in series proximate to the top face, the VCSEL array generating pump beams; a bottom photodetector arranged proximate to the bottom face in alignment with the VCSEL array and the top photodetector array;STDC0645 a routing element arranged in the substrate at 45 to the side faces having a beam splitting lower surface and a reflective upper surface, the lower surface transmitting a major portion of the input beams to the output doped fibre array and reflecting a minor portion of the input beams to the bottom photodetector array, the upper surface reflecting the pump beams to the output doped fibre array; and a processor for adjusting the power level of the pump beams in response to the power levels detected by the top and bottom photodetector arrays so that the gain of the optical amplifier can be selectively controlled.
24. An optical amplifier according to claim 23, further comprising an input microlens array etched in the optical substrate for collimating the input beams.
25. An optical amplifier according to claim 23 or 24, further comprising an output microlens array etched in the optical substrate for coupling the input beams and the pump beams to the output doped fibre array.
26. An optical amplifier according to any one of claims 23 to 25, wherein the bottom photodetector array is flip-chip bonded to the optical substrate.
27. An optical amplifier according to any one of claims 23 to 26, wherein the VCSEL array is flip-chip bonded with an Ultra-Thin Semiconductor (UTS) chip that integrates the top photodetector array. <Desc/Clms Page number 20> 28. An optical amplifier according to any one of claims 23 to 27, wherein the output doped fibre array is an erbium doped fibre array.
29. An optical amplifier according to any one of claims 23 to 28, wherein the optical substrate comprises a glass or sapphire substrate.
30. A method for controlling the optical gains of an optical amplifier, the amplifier comprising at least one optical fibre amplifier and a pump source, the method comprising the steps of: measuring the power of pump beams generated by the pump source and deriving a first signal representative thereof; measuring the power of input optical signals and deriving a second signal representative thereof; estimating the signal gain based on the measured input signal power and pump power, and deriving a third signal representative of the difference between the measured signal gain and the desired signal gain; processing the first, second, and third signals to generate a pump source driving current profile in response to the processed first, second and third signals; and controlling the generation of driving current profile to achieve the desired output power for the pump beam.
31. An optical amplifier substantially as hereinbefore described with reference to the accompanying drawings.
32. A method for controlling the optical gains of an optical amplifier substantially as hereinbefore described with reference to the accompanying drawings.