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Optics Express

Optics Express

  • Editor: J. H. Eberly
  • Vol. 6, Iss. 3 — Jan. 31, 2000
  • pp: 69–74
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All-optical binary counter

Alistair Poustie, R. J. Manning, A. E. Kelly, and K. J. Blow  »View Author Affiliations


Optics Express, Vol. 6, Issue 3, pp. 69-74 (2000)
http://dx.doi.org/10.1364/OE.6.000069


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Abstract

We experimentally demonstrate an all-optical binary counter composed of four semiconductor optical amplifier based all-optical switching gates. The time-of-flight optical circuit operates with bit-differential delays between the exclusive-OR gate used for modulo-2 binary addition and the AND gate used for binary carry detection. A movie of the counter operating in real time is presented.

© Optical Society of America

1. Introduction

Fig. 1. Logic diagram of the binary counter with bit-differential delay. The COUNT memory has a capacity of m bits and the CARRY memory has a capacity of m-1 bits. The delay for the link between the COUNT memory and the AND gate input is m bits. The delay for the link between the CARRY memory and the XOR gate input is m-1 bits. The optical pulses to be counted are input singly with a period of m bits.

2. Experiment

A schematic diagram of the experimental system used for the optical counter is shown in figure 2. The optical pulse sources were jitter-suppressed gain switched distributed feedback (DFB) semiconductor lasers. These gave ~10ps pulses at a repetition rate of 1GHz at wavelengths of λ1=1552nm (DFB#1) and λ2=1534nm (DFB#2). TOAD1 was configured with a relatively wide switching window (~150ps), which is longer than the gain recovery time of the SOA (1/e~80ps), so that a single TOAD could operate as a good all-optical XOR gate [3

3. A. J. Poustie, K. J. Blow, A. E. Kelly, and R. J. Manning, “All-optical parity checker with bit-differential delay,” Opt. Commun. 162, 37–43 (1999). [CrossRef]

,5

5. A. J. Poustie, K. J. Blow, A. E. Kelly, and R. J. Manning, “All-optical full adder with bit-differential delay,” Opt. Commun. 168, 89–93 (1999). [CrossRef]

,9

9. A. J. Poustie, K. J. Blow, R. J. Manning, and A. E. Kelly, “All-optical pseudorandom number generator,” Opt. Commun. 159, 208–214 (1999). [CrossRef]

]. When the SOA recovery time is shorter than the switching window, this allows two temporal switching conditions: one where the signal pulses in the loop experience a differential phase shift due to the recovering gain of the SOA and one where the signal pulses arrive in time before and after the switching pulse. This allows the XOR gate to give an output of ONE when a switching pulse arrives in either of these switching conditions. However if two switching pulses arrive, one in each switching condition, then a very small differential phase shift occurs between the signal pulses in the loop and hence there is no switching of the signal pulses. This gives the required result for XOR that two input ONES gives a ZERO at the output of the gate.

The other TOADs had switching windows of ~50ps and were used as AND gates. At a switching rate of 1GHz, the time between each bit was 1ns. The capacity of the COUNT memory was 297 bits and so the length of optical fibre in the CARRY memory was adjusted to have a capacity of 296 bits i.e. a single bit less than the COUNT memory for bit-differential operation. The length of optical fibre between TOAD1 and TOAD3 was also adjusted to give a delay of 297 bits (~60m) so that for each incoming bit to be counted there was a simultaneous XOR operation in TOAD1 and an AND operation in TOAD3 to generate the CARRY bits. Erbium doped fibre amplifiers (EDFAs) were used to amplify the optical pulses to the TOAD switching energy (~100fJ per pulse) and adjustable optical delay lines were used to control the time of flight of the pulses to achieve all-optical switching in the TOADs.

Fig. 2. Schematic diagram of the experimental all-optical counter architecture. The capacities of the COUNT and CARRY memory loops are 297 bits and 296 bits respectively (1ns per bit). Each TOAD contains an SOA, fibre couplers and fibre polarisation controllers as described in the text. DFB=gain-switched distributed feedback laser, I/P=input, O/P=output, EDFA=erbium doped fibre amplifier, EAM=electroabsorption modulator.

3. Results

Fig. 3. Full optical count field with the LSB on the RHS and the MSB on the LHS. The time separation between pulses is 1ns corresponding to the switching rate of 1GHz and the count rate is ~3.4MHz. The movie (902kb version, 8.57Mb version) shows the real time evolution of the binary count.

In order to show in detail that the counter is counting correctly in binary, figure 4 shows a selective view of the count from 221 to 225. In this real time movie clip it is possible to see the apparent evolution of the count from zero to 25 and the resetting to zero again as the MSB moves out of view of the oscilloscope screen.

Fig. 4. Optical count field from 221 (RHS) to 225 (LHS). The movie (938kb version, 3.67Mb version) shows the real time evolution of the binary count.

Fig. 5. Optical count field from 212 (RHS) to 228 (LHS). The movie (15Mb) shows the real time evolution of the count from <228 to >229 that takes ~160s.

4. Discussion

One of the advantages of time-of-flight designed systems is that they are simply scalable in operation speed to the fastest switching speed of the logic gates [10

10. H. F. Jordan, V. P. Heuringand, and R. Feuerstein, “Optoelectronic time-of-flight design and the demonstration of an all-optical, stored program, digital computer,” Proc. IEEE 82, 1678–1689 (1994). [CrossRef]

]. With SOA based gates, ~100Gbit/s AND gate operation has been reported [11

11. K. L. Hall and K. A. Rauschenbach, “100Gbit/s bitwise logic,” Opt. Lett. 23, 1271–1273 (1998). [CrossRef]

,12

12. A.E. Kelly, I. D. Phillips, R. J. Manning, A. D. Ellis, D. Nesset, D. G. Moodie, and R. Kashyap, “80Gbit/s all-optical regenerative wavelength conversion using semiconductor optical amplifier based interferometer,” Electron. Lett. 35, 1477–1478 (1999). [CrossRef]

] with similar switching energies to those required here. However, at these switching rates it is likely that the XOR operation will require more than a single TOAD, but we have previously demonstrated how this is possible using two AND gates and an OR gate [13

13. A. J. Poustie, K. J. Blow, A. E. Kelly, and R. J. Manning, “All-optical binary half-adder,” Opt. Commun. 156, 22–26 (1998). [CrossRef]

]. Reducing the capacities of the memories and hence increasing the count rate will require the time-of-flight latency to be reduced. This should be achievable using integrated SOA based all-optical switches [14

14. E. Jahn, N. Agrawal, W. Peiper, H. J. Ehrke, D. Franke, W. Furst, and C. M. Weinert, “Monolithically integrated nonlinear Sagnac interferometer and its application as a 20 Gbit/s all-optical demultiplexer,” Electron. Lett. 32, 782–784 (1996). [CrossRef]

17

17. J. Leuthold, P. A. Besse, J. Eckner, E. Gamper, M. Dulk, and H. Melchior, “All-optical space switches with gain and principally ideal extinction ratios,” IEEE J. Quantum Electron. 34, 622–633 (1998). [CrossRef]

] and using planar silica interconnects between the switching gates [18

18. J. Sasaki, H. Hatakeyama, T. Tamanuki, S. Kitamura, M. Yamaguchi, N. Kitamura, T. Shimoda, M. Kitamura, T. Kato, and M. Itoh, , “Hybrid integrated 4×4 optical matrix switch using self-aligned semiconductor optical amplifier gate arrays and silica planar lightwave circuit,” Electron. Lett. 34, 986–987 (1998). [CrossRef]

]. If the latency can be sufficiently reduced then it may be possible to create truly bit-serial optical delays so that the bit-differential technique described here would not be required. Optoelectronic counters based on true bit-serial design have been demonstrated previously [19

19. A. F. Benner, J. Bowman, T. Erkkila, R. J. Feuerstein, V. P. Heuring, H. F. Jordan, J. Sauer, and T. Soukup, “Digital optical counter using directional coupler switches,” Appl. Opt. 30, 4179–4189 (1991). [CrossRef] [PubMed]

].

5. Conclusions

In conclusion, we have successfully demonstrated an all-optical binary counter with bit-differential delay. In common with other time-of-flight designed, SOA based optical processing systems, this all-optical architecture should be scaleable in operating speed to the fastest switching speed of the all-optical gates.

Acknowledgements

The authors would like to thank Colin Ford and Dave Moodie at BT Adastral Park for the packaged SOAs and electroabsorption modulator. We also thank Richard Jeffery at BT for his assistance with the multimedia file preparation.

References and links

1.

D. Cotter, J. K. Lucek, P. Gunning, D. G. Moodie, A. J. Poustie, K. J. Blow, and R. J. Manning, “Ultrafast networks using high-speed RZ optical pulses for transmission, routing and processing” in New Trends in Optical Soliton Communications, A. Hasegawa, ed. (Kluwer Academic, Dordrecht, 1998).

2.

D. Cotter and A. D. Ellis, “Asynchronous digital optical regeneration and networks,” IEEE J. Lightwave Technol. 16, 2068–2080 (1998). [CrossRef]

3.

A. J. Poustie, K. J. Blow, A. E. Kelly, and R. J. Manning, “All-optical parity checker with bit-differential delay,” Opt. Commun. 162, 37–43 (1999). [CrossRef]

4.

A. J. Poustie, K. J. Blow, and R. J. Manning, “All-optical regenerative memory for long term data storage,” Opt. Commun. 140, 184–186 (1997). [CrossRef]

5.

A. J. Poustie, K. J. Blow, A. E. Kelly, and R. J. Manning, “All-optical full adder with bit-differential delay,” Opt. Commun. 168, 89–93 (1999). [CrossRef]

6.

J. P. Sokoloff, P. R. Prucnal, I. Glesk, and M. Kane, “A Terahertz optical asymmetric demultiplexer (TOAD),” IEEE Phot. Tech. Lett. 5, 787–790 (1993). [CrossRef]

7.

K. L. Hall, J. P. Donnelly, S. H. Groves, C. I. Fennelly, R. A. Bailey, and A. Napoleone, “40Gbit/s all-optical circulating shift register with an inverter,” Opt. Lett. 22, 1479–1481 (1997). [CrossRef]

8.

A. J. Poustie, R. J. Manning, and K. J. Blow, “All-optical circulating shift register using a semiconductor optical amplifier in a fibre loop mirror,” Electron. Lett. 32, 1215–1216 (1996). [CrossRef]

9.

A. J. Poustie, K. J. Blow, R. J. Manning, and A. E. Kelly, “All-optical pseudorandom number generator,” Opt. Commun. 159, 208–214 (1999). [CrossRef]

10.

H. F. Jordan, V. P. Heuringand, and R. Feuerstein, “Optoelectronic time-of-flight design and the demonstration of an all-optical, stored program, digital computer,” Proc. IEEE 82, 1678–1689 (1994). [CrossRef]

11.

K. L. Hall and K. A. Rauschenbach, “100Gbit/s bitwise logic,” Opt. Lett. 23, 1271–1273 (1998). [CrossRef]

12.

A.E. Kelly, I. D. Phillips, R. J. Manning, A. D. Ellis, D. Nesset, D. G. Moodie, and R. Kashyap, “80Gbit/s all-optical regenerative wavelength conversion using semiconductor optical amplifier based interferometer,” Electron. Lett. 35, 1477–1478 (1999). [CrossRef]

13.

A. J. Poustie, K. J. Blow, A. E. Kelly, and R. J. Manning, “All-optical binary half-adder,” Opt. Commun. 156, 22–26 (1998). [CrossRef]

14.

E. Jahn, N. Agrawal, W. Peiper, H. J. Ehrke, D. Franke, W. Furst, and C. M. Weinert, “Monolithically integrated nonlinear Sagnac interferometer and its application as a 20 Gbit/s all-optical demultiplexer,” Electron. Lett. 32, 782–784 (1996). [CrossRef]

15.

E. Jahn, N. Agrawal, M. Arbert, H. J. Ehrke, D. Franke, R. Ludwig, W. Peiper, H. G. Weber, and C. M. Weinert, “40 Gbit/s all-optical demultiplexing using a monolithically integrated Mach-Zehnder interferometer with semiconductor laser amplifiers,” Electron. Lett. 31, 1857–1858 (1995). [CrossRef]

16.

B. Mikkelsen, T. Durhuus, C. Joergensen, R. J. S. Pedersen, S. L. Danielsen, K. E. Stubkjaer, M. Gustavsson, W. Van Berlo, and M. Janson, “10Gbit/s wavelength convertoer realised by monolithic integration of semiconductor optical amplifiers and Michelson interferometer,” Postdeadline paper, Proceedings ECOC ’94 Florence, 1994.

17.

J. Leuthold, P. A. Besse, J. Eckner, E. Gamper, M. Dulk, and H. Melchior, “All-optical space switches with gain and principally ideal extinction ratios,” IEEE J. Quantum Electron. 34, 622–633 (1998). [CrossRef]

18.

J. Sasaki, H. Hatakeyama, T. Tamanuki, S. Kitamura, M. Yamaguchi, N. Kitamura, T. Shimoda, M. Kitamura, T. Kato, and M. Itoh, , “Hybrid integrated 4×4 optical matrix switch using self-aligned semiconductor optical amplifier gate arrays and silica planar lightwave circuit,” Electron. Lett. 34, 986–987 (1998). [CrossRef]

19.

A. F. Benner, J. Bowman, T. Erkkila, R. J. Feuerstein, V. P. Heuring, H. F. Jordan, J. Sauer, and T. Soukup, “Digital optical counter using directional coupler switches,” Appl. Opt. 30, 4179–4189 (1991). [CrossRef] [PubMed]

OCIS Codes
(200.4560) Optics in computing : Optical data processing
(200.4660) Optics in computing : Optical logic

ToC Category:
Research Papers

History
Original Manuscript: December 8, 1999
Published: January 31, 2000

Citation
Alistair Poustie, Robert Manning, A. Kelly, and Keith Blow, "All-optical binary counter," Opt. Express 6, 69-74 (2000)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-6-3-69


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References

  1. D. Cotter, J. K. Lucek, P. Gunning, D. G. Moodie, A. J. Poustie, K. J. Blow, R. J. Manning, "Ultrafast networks using high-speed RZ optical pulses for transmission, routing and processing" in New Trends in Optical Soliton Communications, A. Hasegawa, ed. (Kluwer Academic, Dordrecht, 1998).
  2. D. Cotter and A. D. Ellis, "Asynchronous digital optical regeneration and networks," IEEE J. Lightwave Technol. 16, 2068-2080 (1998). [CrossRef]
  3. A. J. Poustie, K. J. Blow, A. E. Kelly and R. J. Manning, "All-optical parity checker with bit-differential delay," Opt. Commun. 162, 37-43 (1999). [CrossRef]
  4. A. J. Poustie, K. J. Blow and R. J. Manning, "All-optical regenerative memory for long term data storage," Opt. Commun. 140, 184-186 (1997). [CrossRef]
  5. A. J. Poustie, K. J. Blow, A. E. Kelly and R. J. Manning, "All-optical full adder with bit-differential delay," Opt. Commun. 168, 89-93 (1999). [CrossRef]
  6. J. P. Sokoloff, P. R. Prucnal, I. Glesk and M. Kane, "A Terahertz optical asymmetric demultiplexer (TOAD)," IEEE Phot. Tech. Lett. 5, 787-790 (1993). [CrossRef]
  7. K. L. Hall, J. P. Donnelly, S. H. Groves, C. I. Fennelly, R. A. Bailey and A. Napoleone, "40Gbit/s all-optical circulating shift register with an inverter," Opt. Lett. 22, 1479-1481 (1997). [CrossRef]
  8. A. J. Poustie, R. J. Manning and K. J. Blow, "All-optical circulating shift register using a semiconductor optical amplifier in a fibre loop mirror," Electron. Lett. 32, 1215-1216 (1996). [CrossRef]
  9. A. J. Poustie, K. J. Blow, R. J. Manning and A. E. Kelly, "All-optical pseudorandom number generator," Opt. Commun. 159, 208-214 (1999). [CrossRef]
  10. H. F. Jordan, V. P. Heuringand R. Feuerstein, "Optoelectronic time-of-flight design and the demonstration of an all-optical, stored program, digital computer," Proc. IEEE 82, 1678-1689 (1994). [CrossRef]
  11. K. L. Hall and K. A. Rauschenbach, "100Gbit/s bitwise logic," Opt. Lett. 23, 1271-1273 (1998). [CrossRef]
  12. A.E. Kelly, I. D. Phillips, R. J. Manning, A. D. Ellis, D. Nesset, D. G. Moodie and R. Kashyap, "80Gbit/s all-optical regenerative wavelength conversion using semiconductor optical amplifier based interferometer," Electron. Lett. 35, 1477-1478 (1999). [CrossRef]
  13. A. J. Poustie, K. J. Blow, A. E. Kelly and R. J. Manning, "All-optical binary half-adder," Opt. Commun. 156, 22-26 (1998). [CrossRef]
  14. E. Jahn, N. Agrawal, W. Peiper, H. J. Ehrke, D. Franke, W. Furst and C. M. Weinert, "Monolithically integrated nonlinear Sagnac interferometer and its application as a 20 Gbit/s all-optical demultiplexer," Electron. Lett. 32, 782-784 (1996). [CrossRef]
  15. E. Jahn, N. Agrawal, M. Arbert, H. J. Ehrke, D. Franke, R. Ludwig, W. Peiper, H. G. Weber and C. M. Weinert, "40 Gbit/s all-optical demultiplexing using a monolithically integrated Mach-Zehnder interferometer with semiconductor laser amplifiers," Electron. Lett. 31, 1857-1858 (1995). [CrossRef]
  16. B. Mikkelsen, T. Durhuus, C. Joergensen, R. J. S. Pedersen, S. L. Danielsen, K. E. Stubkjaer, M. Gustavsson, W. Van Berlo and M. Janson, "10Gbit/s wavelength convertoer realised by monolithic integration of semiconductor optical amplifiers and Michelson interferometer," Postdeadline paper, Proceedings ECOC '94 Florence, 1994.
  17. J. Leuthold, P. A. Besse, J. Eckner, E. Gamper, M. Dulk and H. Melchior, "All-optical space switches with gain and principally ideal extinction ratios," IEEE J. Quantum Electron. 34, 622-633 (1998). [CrossRef]
  18. J. Sasaki, H. Hatakeyama, T. Tamanuki, S. Kitamura, M. Yamaguchi, N. Kitamura, T. Shimoda, M. Kitamura, T. Kato and M. Itoh, , "Hybrid integrated 4x4 optical matrix switch using self-aligned semiconductor optical amplifier gate arrays and silica planar lightwave circuit," Electron. Lett. 34, 986-987 (1998). [CrossRef]
  19. A. F. Benner, J. Bowman, T. Erkkila, R. J. Feuerstein, V. P. Heuring, H. F. Jordan, J. Sauer and T. Soukup, "Digital optical counter using directional coupler switches," Appl. Opt. 30, 4179-4189 (1991). [CrossRef] [PubMed]

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