Abstract

We demonstrate a field programmable gate array (FPGA) based optical orthogonal frequency division multiplexing (OFDM) transmitter implementing real time digital signal processing at a sample rate of 21.4 GS/s. The QPSK-OFDM signal is generated using an 8 bit, 128 point inverse fast Fourier transform (IFFT) core, performing one transform per clock cycle at a clock speed of 167.2 MHz and can be deployed with either a direct-detection or a coherent receiver. The hardware design and the main digital signal processing functions are described, and we show that the main performance limitation is due to the low (4-bit) resolution of the digital-to-analog converter (DAC) and the 8-bit resolution of the IFFT core used. We analyze the back-to-back performance of the transmitter generating an 8.36 Gb/s optical single sideband (SSB) OFDM signal using digital up-conversion, suitable for direct-detection. Additionally, we use the device to transmit 8.36 Gb/s SSB OFDM signals over 200 km of uncompensated standard single mode fiber achieving an overall BER<10−3.

© 2009 OSA

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  1. S. L. Jansen, I. Morita, K. Forozesh, S. Randel, D. van den Borne, and H. Tanaka, ‘Optical OFDM, a hype or is it for real?’, in Proc. Europ. Conference on Optical Comm. (ECOC), paper Mo.3.E.3 (2008)
  2. W. Shieh, Q. Yang, and Y. Ma, “107 Gb/s coherent optical OFDM transmission over 1000-km SSMF fiber using orthogonal band multiplexing,” Opt. Express 16(9), 6378–6386 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-9-6378 .
    [CrossRef] [PubMed]
  3. S. L. Jansen, A. Al Amin, H. Takahashi, I. Morita, and H. Tanaka, “132.2-Gb/s PDM-8QAM-OFDM transmission at 4-b/s/Hz spectral efficiency,” Photon. Technol. Lett. 21(12), 802–804 (2009).
    [CrossRef]
  4. A. J. Lowery, L. B. Du, and J. Armstrong,“Armstrong, ‘Performance of optical OFDM in ultralong-haul WDM lightwave systems’,” J. Lightwave Technol. 25(1), 131–138 (2007).
    [CrossRef]
  5. B. J. C. Schmidt, A. J. Lowery, and J. Armstrong, “Experimental demonstrations of electronic dispersion compensation for long-haul transmission using direct-detection optical OFDM,” J. Lightwave Technol. 26(1), 196–203 (2008).
    [CrossRef]
  6. Y. Benlachtar, G. Gavioli, V. Mikhailov, and R. I. Killey, “Experimental investigation of SPM in long-haul direct-detection OFDM systems,” Opt. Express 16(20), 15477–15482 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-20-15477 .
    [CrossRef] [PubMed]
  7. Y. Benlachtar, R.I. Killey,'Investigation of 11.1Gbit/s direct-detection OFDM QAM-16 transmission over 1600km of uncompensated fiber', in Proc. Optical Fiber Comm. (OFC), paper OWM5 (2009).
  8. B. J. C. Schmidt, Z. Zan, L. B. Du, A.J. Lowery, ‘100Gbit/s transmission using single-band direct-detection optical OFDM’, in Proc. Optical Fiber Comm.(OFC), paper PDPC3 (2009).
  9. D. Qian, N. Cvijetic, J. Hu, T. Wang, ‘108 Gb/s OFDMA-PON with polarization multiplexing and direct-detection’, in Proc. Optical Fiber Comm.(OFC), paper PDPD5 (2009).
  10. H. Yang, S. C. J. Lee, E. Tangdiongga, F. Breyer, S. Randel, A. M. J. Koonen, ‘40 Gb/s transmission over 100m graded-index plastic optical fiber based on discrete multitone modulation’, in Proc. Optical Fiber Comm.(OFC), paper PDPD8 (2009).
  11. J. M. Tang, P. M. Lane, and K. A. Shore, “High-speed transmission of adaptively modulated optical OFDM signals over multimode fibers using directly modulated DFBs,” J. Lightwave Technol. 24(1), 429–441 (2006).
    [CrossRef]
  12. Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express 17(10), 7985–7992 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-10-7985 .
    [CrossRef] [PubMed]
  13. B. J. C. Schmidt, A. J. Lowery, L. B. Du, 'Low sample rate transmitter for direct-detection optical OFDM', in Proc. Optical Fiber Comm.(OFC), paper OWM4 (2009).
  14. S. L. Jansen, I. Morita, T. C. W. Schenk, and H. Tanaka, “121.9-Gb/s PDM-OFDM transmission with 2-b/s/Hz spectral efficiency over 1000 km of SSMF,” J. Lightwave Technol. 27(3), 177–188 (2009).
    [CrossRef]
  15. P. M. Watts, R. Waegemans, Y. Benlachtar, V. Mikhailov, P. Bayvel, and R. I. Killey, “10.7 Gb/s transmission over 1200 km of standard single-mode fiber by electronic predistortion using FPGA-based real-time digital signal processing,” Opt. Express 16(16), 12171–12180 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-16-12171 .
    [CrossRef] [PubMed]
  16. P. Watts, R. Waegemans, M. Glick, P. Bayvel, and R. Killey, “An FPGA-based optical transmitter design using real-time DSP for advanced signal formats and electronic predistortion,” J. Lightwave Technol. 25(10), 3089–3099 (2007).
    [CrossRef]
  17. P. A. Milder, F. Franchetti, J. C. Hoe, and M. Püschel, ‘Formal datapath representation and manipulation for implementing DSP transforms’, in Proc. Design Automation Conference (DAC), 385–390 (2008)
  18. G. Nordin, P. A. Milder, J. C. Hoe, and M. Püschel, ‘Automatic generation of customized discrete Fourier transform IPs’ in Proc. Design Automation Conference (DAC), 471–474 (2005)
  19. R.A. Shafik, S. Rahman, A.H.M. Razibul Islam, 'On the extended relationships among EVM, BER and SNR as performance metrics', in Proc. Int. Conf. on Elec. and Computer Eng.(ICECE), 408 - 411 (2006).
  20. A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express 14(6), 2079–2084 (2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-6-2079 .
    [CrossRef] [PubMed]
  21. H. Ochiai and H. Imai, “Performance analysis of deliberately clipped OFDM signals,” IEEE Trans. Commun. 50(1), 89–101 (2002).
    [CrossRef]
  22. R. Waegemans, S. Herbst, L. Holbein, P. Watts, P. Bayvel, C. Fürst, and R. I. Killey, “10.7 Gb/s electronic predistortion transmitter using commercial FPGAs and D/A converters implementing real-time DSP for chromatic dispersion and SPM compensation,” Opt. Express 17(10), 8630–8640 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-10-8630 .
    [CrossRef] [PubMed]

2009 (4)

2008 (4)

2007 (2)

2006 (2)

2002 (1)

H. Ochiai and H. Imai, “Performance analysis of deliberately clipped OFDM signals,” IEEE Trans. Commun. 50(1), 89–101 (2002).
[CrossRef]

Al Amin, A.

S. L. Jansen, A. Al Amin, H. Takahashi, I. Morita, and H. Tanaka, “132.2-Gb/s PDM-8QAM-OFDM transmission at 4-b/s/Hz spectral efficiency,” Photon. Technol. Lett. 21(12), 802–804 (2009).
[CrossRef]

Armstrong, J.

Bayvel, P.

Benlachtar, Y.

Chen, S.

Du, L. B.

Fürst, C.

Gavioli, G.

Glick, M.

Herbst, S.

Holbein, L.

Imai, H.

H. Ochiai and H. Imai, “Performance analysis of deliberately clipped OFDM signals,” IEEE Trans. Commun. 50(1), 89–101 (2002).
[CrossRef]

Jansen, S. L.

S. L. Jansen, A. Al Amin, H. Takahashi, I. Morita, and H. Tanaka, “132.2-Gb/s PDM-8QAM-OFDM transmission at 4-b/s/Hz spectral efficiency,” Photon. Technol. Lett. 21(12), 802–804 (2009).
[CrossRef]

S. L. Jansen, I. Morita, T. C. W. Schenk, and H. Tanaka, “121.9-Gb/s PDM-OFDM transmission with 2-b/s/Hz spectral efficiency over 1000 km of SSMF,” J. Lightwave Technol. 27(3), 177–188 (2009).
[CrossRef]

Killey, R.

Killey, R. I.

Lane, P. M.

Lowery, A. J.

Ma, Y.

Mikhailov, V.

Morita, I.

S. L. Jansen, I. Morita, T. C. W. Schenk, and H. Tanaka, “121.9-Gb/s PDM-OFDM transmission with 2-b/s/Hz spectral efficiency over 1000 km of SSMF,” J. Lightwave Technol. 27(3), 177–188 (2009).
[CrossRef]

S. L. Jansen, A. Al Amin, H. Takahashi, I. Morita, and H. Tanaka, “132.2-Gb/s PDM-8QAM-OFDM transmission at 4-b/s/Hz spectral efficiency,” Photon. Technol. Lett. 21(12), 802–804 (2009).
[CrossRef]

Ochiai, H.

H. Ochiai and H. Imai, “Performance analysis of deliberately clipped OFDM signals,” IEEE Trans. Commun. 50(1), 89–101 (2002).
[CrossRef]

Schenk, T. C. W.

Schmidt, B. J. C.

Shieh, W.

Shore, K. A.

Takahashi, H.

S. L. Jansen, A. Al Amin, H. Takahashi, I. Morita, and H. Tanaka, “132.2-Gb/s PDM-8QAM-OFDM transmission at 4-b/s/Hz spectral efficiency,” Photon. Technol. Lett. 21(12), 802–804 (2009).
[CrossRef]

Tanaka, H.

S. L. Jansen, A. Al Amin, H. Takahashi, I. Morita, and H. Tanaka, “132.2-Gb/s PDM-8QAM-OFDM transmission at 4-b/s/Hz spectral efficiency,” Photon. Technol. Lett. 21(12), 802–804 (2009).
[CrossRef]

S. L. Jansen, I. Morita, T. C. W. Schenk, and H. Tanaka, “121.9-Gb/s PDM-OFDM transmission with 2-b/s/Hz spectral efficiency over 1000 km of SSMF,” J. Lightwave Technol. 27(3), 177–188 (2009).
[CrossRef]

Tang, J. M.

Waegemans, R.

Watts, P.

Watts, P. M.

Yang, Q.

IEEE Trans. Commun. (1)

H. Ochiai and H. Imai, “Performance analysis of deliberately clipped OFDM signals,” IEEE Trans. Commun. 50(1), 89–101 (2002).
[CrossRef]

J. Lightwave Technol. (5)

Opt. Express (6)

W. Shieh, Q. Yang, and Y. Ma, “107 Gb/s coherent optical OFDM transmission over 1000-km SSMF fiber using orthogonal band multiplexing,” Opt. Express 16(9), 6378–6386 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-9-6378 .
[CrossRef] [PubMed]

P. M. Watts, R. Waegemans, Y. Benlachtar, V. Mikhailov, P. Bayvel, and R. I. Killey, “10.7 Gb/s transmission over 1200 km of standard single-mode fiber by electronic predistortion using FPGA-based real-time digital signal processing,” Opt. Express 16(16), 12171–12180 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-16-12171 .
[CrossRef] [PubMed]

Y. Benlachtar, G. Gavioli, V. Mikhailov, and R. I. Killey, “Experimental investigation of SPM in long-haul direct-detection OFDM systems,” Opt. Express 16(20), 15477–15482 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-20-15477 .
[CrossRef] [PubMed]

Q. Yang, S. Chen, Y. Ma, and W. Shieh, “Real-time reception of multi-gigabit coherent optical OFDM signals,” Opt. Express 17(10), 7985–7992 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-10-7985 .
[CrossRef] [PubMed]

R. Waegemans, S. Herbst, L. Holbein, P. Watts, P. Bayvel, C. Fürst, and R. I. Killey, “10.7 Gb/s electronic predistortion transmitter using commercial FPGAs and D/A converters implementing real-time DSP for chromatic dispersion and SPM compensation,” Opt. Express 17(10), 8630–8640 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-10-8630 .
[CrossRef] [PubMed]

A. J. Lowery and J. Armstrong, “Orthogonal-frequency-division multiplexing for dispersion compensation of long-haul optical systems,” Opt. Express 14(6), 2079–2084 (2006), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-6-2079 .
[CrossRef] [PubMed]

Photon. Technol. Lett. (1)

S. L. Jansen, A. Al Amin, H. Takahashi, I. Morita, and H. Tanaka, “132.2-Gb/s PDM-8QAM-OFDM transmission at 4-b/s/Hz spectral efficiency,” Photon. Technol. Lett. 21(12), 802–804 (2009).
[CrossRef]

Other (9)

Y. Benlachtar, R.I. Killey,'Investigation of 11.1Gbit/s direct-detection OFDM QAM-16 transmission over 1600km of uncompensated fiber', in Proc. Optical Fiber Comm. (OFC), paper OWM5 (2009).

B. J. C. Schmidt, Z. Zan, L. B. Du, A.J. Lowery, ‘100Gbit/s transmission using single-band direct-detection optical OFDM’, in Proc. Optical Fiber Comm.(OFC), paper PDPC3 (2009).

D. Qian, N. Cvijetic, J. Hu, T. Wang, ‘108 Gb/s OFDMA-PON with polarization multiplexing and direct-detection’, in Proc. Optical Fiber Comm.(OFC), paper PDPD5 (2009).

H. Yang, S. C. J. Lee, E. Tangdiongga, F. Breyer, S. Randel, A. M. J. Koonen, ‘40 Gb/s transmission over 100m graded-index plastic optical fiber based on discrete multitone modulation’, in Proc. Optical Fiber Comm.(OFC), paper PDPD8 (2009).

S. L. Jansen, I. Morita, K. Forozesh, S. Randel, D. van den Borne, and H. Tanaka, ‘Optical OFDM, a hype or is it for real?’, in Proc. Europ. Conference on Optical Comm. (ECOC), paper Mo.3.E.3 (2008)

B. J. C. Schmidt, A. J. Lowery, L. B. Du, 'Low sample rate transmitter for direct-detection optical OFDM', in Proc. Optical Fiber Comm.(OFC), paper OWM4 (2009).

P. A. Milder, F. Franchetti, J. C. Hoe, and M. Püschel, ‘Formal datapath representation and manipulation for implementing DSP transforms’, in Proc. Design Automation Conference (DAC), 385–390 (2008)

G. Nordin, P. A. Milder, J. C. Hoe, and M. Püschel, ‘Automatic generation of customized discrete Fourier transform IPs’ in Proc. Design Automation Conference (DAC), 471–474 (2005)

R.A. Shafik, S. Rahman, A.H.M. Razibul Islam, 'On the extended relationships among EVM, BER and SNR as performance metrics', in Proc. Int. Conf. on Elec. and Computer Eng.(ICECE), 408 - 411 (2006).

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Figures (7)

Fig. 1
Fig. 1

Conceptual design of an optical OFDM transmitter. S/P: serial to parallel, LPF: low-pass filter, MZM: Mach-Zehnder modulator, DML: directly modulated laser

Fig. 2
Fig. 2

Transmitter design (a) top level hardware (b) FPGA functions

Fig. 3
Fig. 3

Experimentally measured spectra of (a) 10.7 Gb/s SSB OFDM (b) 8.36 Gb/s SSB OFDM (c) 8.36 Gb/s SSB OFDM with a 7.5 GHz low pass (smoothing) filter. Simulated spectra of (d) 8.36 Gb/s QPSK-OFDM using 8-bit IFFT (e) 8.36 Gb/s QPSK-OFDM using 12-bit IFFT (f) 8.36 Gb/s QPSK-OFDM using 16-bit IFFT

Fig. 4
Fig. 4

(a) Calculated EVM vs clipping ratio for different DAC effective number of bits, (b) Experimentally measured constellation without clipping, (c) Constellation with 4.5 dB clipping ratio, (d) Constellation with 4.5 dB clipping ratio showing only the lowest and highest frequency OFDM channels (e) Constellation (4.5 dB clipping ratio) after post-equalization (by offline processing of the signal).

Fig. 5
Fig. 5

(a) EVM per channel (b) Relationship between BER and EVM (assuming an ideal receiver)

Fig. 6
Fig. 6

(a) Experimental setup. Inset: SSB OFDM optical spectrum (b) back-to-back constellation (c) received constellation (unequalized) (d) received constellation (equalized).

Fig. 7
Fig. 7

(a) Average EVM of the system (circles) and EVM of the first OFDM sub-channel (triangles) against OSNR (b) EVM per channel for back-to-back and after 200 km of transmission

Metrics