Abstract

We propose a novel optical 45° hybrid employing a 2 × 8 paired interference based multimode interference (MMI) coupler, three phase shifters and three 2 × 2 optical couplers. Since the proposed 45° hybrid can demodulate an 8-ary differential phase shift keyed (8-DPSK) signal with only one delayed Mach-Zehnder interferometer (DMZI), the demodulator has simpler configuration and much smaller device dimensions than conventional 8-DPSK demodulators consisting of four pairs of DMZIs and 2 × 2 optical couplers. We calculate and experimentally demonstrate octagonal phase response of the proposed 45° hybrid with a relative phase deviation of < ± 5° over 32-nm-wide spectral range.

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References

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  1. J. G. Proakis, “Digital communications,” 4th ed., (New York: McGraw-Hill, 2000).
  2. M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
    [CrossRef]
  3. T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
    [CrossRef]
  4. L. Christen, S. R. Nuccio, W. Xiaoxia, and A. E. Willner, “Polarization-based 43 Gb/s RZ-DQPSK receiver design employing a single delay-line interferometer,” Proc. CLEO 2007, CMJJ6, 2007.
  5. H. Yoon, D. Lee, and N. Park, “Performance comparison of optical 8-ary differential phase-shift keying systems with different electrical decision schemes,” Opt. Express 13(2), 371–376 (2005).
    [CrossRef] [PubMed]
  6. M. Seimetz, M. Noelle, and E. Patzak, “Optical systems with high-order DPSK and star QAM modulation based on interferometric direct detection,” J. Lightwave Technol. 25(6), 1515–1530 (2007).
    [CrossRef]
  7. M. Noelle, M. Seimetz, and E. Patzak, “System performance of high-order optical DPSK and star QAM modulation for direct detection analyzed by semi-analytical BER estimation,” J. Lightwave Technol. 27(19), 4319–4329 (2009).
    [CrossRef]
  8. L. B. Soldano and E. C. M. Pennings, “Optical multimode interference devices based on self-imaging: Principles and Applications,” J. Lightwave Technol. 13(4), 615–627 (1995).
    [CrossRef]
  9. M. Bachmann, P. A. Besse, and H. Melchior, “Overlapping image multimode interference couplers with a reduced number of self-images for uniform and nonuniform power splitting,” Appl. Opt. 34(30), 6898–6910 (1995).
    [CrossRef] [PubMed]

2009 (1)

2007 (1)

2005 (1)

2004 (1)

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

2000 (1)

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

1995 (2)

L. B. Soldano and E. C. M. Pennings, “Optical multimode interference devices based on self-imaging: Principles and Applications,” J. Lightwave Technol. 13(4), 615–627 (1995).
[CrossRef]

M. Bachmann, P. A. Besse, and H. Melchior, “Overlapping image multimode interference couplers with a reduced number of self-images for uniform and nonuniform power splitting,” Appl. Opt. 34(30), 6898–6910 (1995).
[CrossRef] [PubMed]

Bachmann, M.

Bachus, E. J.

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

Besse, P. A.

Cai, J. X.

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

Caspar, C.

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

Davidson, C. R.

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

Foursa, D.

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

Hanik, N.

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

Heimes, N.

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

Konitzer, M.

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

Lee, D.

Melchior, H.

Nissov, M.

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

Noelle, M.

Park, N.

Patzak, E.

Pennings, E. C. M.

L. B. Soldano and E. C. M. Pennings, “Optical multimode interference devices based on self-imaging: Principles and Applications,” J. Lightwave Technol. 13(4), 615–627 (1995).
[CrossRef]

Pilipetskii, A.

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

Rohde, M.

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

Seimetz, M.

Soldano, L. B.

L. B. Soldano and E. C. M. Pennings, “Optical multimode interference devices based on self-imaging: Principles and Applications,” J. Lightwave Technol. 13(4), 615–627 (1995).
[CrossRef]

Tokle, T.

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

Yoon, H.

Appl. Opt. (1)

Electron. Lett. (2)

M. Rohde, C. Caspar, N. Hanik, N. Heimes, M. Konitzer, and E. J. Bachus, “Robustness of DPSK direct detection transmission format in standard fiber WDM systems,” Electron. Lett. 36(17), 1483–1484 (2000).
[CrossRef]

T. Tokle, C. R. Davidson, M. Nissov, J. X. Cai, D. Foursa, and A. Pilipetskii, “6500 km transmission of RZ-DQPSK WDM signals,” Electron. Lett. 40(7), 444–445 (2004).
[CrossRef]

J. Lightwave Technol. (3)

Opt. Express (1)

Other (2)

J. G. Proakis, “Digital communications,” 4th ed., (New York: McGraw-Hill, 2000).

L. Christen, S. R. Nuccio, W. Xiaoxia, and A. E. Willner, “Polarization-based 43 Gb/s RZ-DQPSK receiver design employing a single delay-line interferometer,” Proc. CLEO 2007, CMJJ6, 2007.

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Figures (7)

Fig. 1
Fig. 1

Schematic diagram of the proposed optical 45° hybrid consisting of a PI-based 2 × 8 MMI coupler, three pairs of phase shifters and 2 × 2 MMI couplers.

Fig. 2
Fig. 2

Schematic diagrams of 8-DPSK demodulators employing a conventional scheme (a) the proposed scheme (b).

Fig. 3
Fig. 3

Analytically calculated transmission spectra of the proposed schemes with the optimized phase shifters (a) and without the phase shifters (b) as a function of the phase difference between the two input signals (ΔΦ = ϕS1– ϕS2)

Fig. 4
Fig. 4

Numerically simulated transmission spectra as a function of ΔΦ (a) and Δϕ of the proposed 45° hybrid within the C-band spectral range

Fig. 5
Fig. 5

Top-views of the fabricated 8-DPSK demodulator scheme (a), the proposed 45° hybrid (b) and the magnified view around the phase shifters (c)

Fig. 6
Fig. 6

Measured transmission spectra of the fabricated 8-DPSK demodulator scheme within the C-band spectral range

Fig. 7
Fig. 7

Magnified view of the measured spectra shown in Fig. 6 (a) and the experimentally estimated relative phase deviation from the octagonal phase relation (Δϕ) within the C-band spectral range (b).

Tables (1)

Tables Icon

Table 1 Parameters of each phase shifter in the proposed 45° hybrid

Equations (11)

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ϕ 1 , y = π 32 y ( 18 + 2 ρ 3 y ) 17 32 π ρ
ϕ 2 , y = π 32 [ 2 ( 1 + ρ ) y 3 y 2 ρ ] + ( ρ 3 2 ) π
E S 1 = P S 1 e j ω S 1 t e j φ S 1
E S 2 = P S 2 e j ω S 2 t e j φ S 2
[ E 1 E 2 E 3 E 4 E 5 E 6 E 7 E 8 ] = [ T 2 ] [ T P S ] [ T 1 ] [ E S 1 E S 2 0 0 0 0 0 0 ]
[ T 1 ] = κ 28 [ 1 1 0 0 0 0 0 0 e j π 8 e j 7 π 8 0 0 0 0 0 0 e j 3 π 8 e j 5 π 8 0 0 0 0 0 0 1 1 0 0 0 0 0 0 1 1 0 0 0 0 0 0 e j 5 π 8 e j 3 π 8 0 0 0 0 0 0 e j 7 π 8 e j π 8 0 0 0 0 0 0 1 1 0 0 0 0 0 0 ]
[ T P S ] = [ 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 e + j θ 6 0 0 0 0 0 0 0 0 e + j θ 5 0 0 0 0 0 0 0 0 e + j θ 4 0 0 0 0 0 0 0 0 e + j θ 3 0 0 0 0 0 0 0 0 e + j θ 2 0 0 0 0 0 0 0 0 e + j θ 1 ]
[ T 2 ] = [ 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 κ A e j π 2 κ A 0 0 0 0 0 0 e j π 2 κ A 1 κ A 0 0 0 0 0 0 0 0 1 κ B e j π 2 κ B 0 0 0 0 0 0 e j π 2 κ B 1 κ B 0 0 0 0 0 0 0 0 1 κ C e j π 2 κ C 0 0 0 0 0 0 e j π 2 κ C 1 κ C ]
θ 2 θ 1 = π 8 ± ( p π ) p : positive integer
θ 4 θ 3 = 5 π 8 ± ( p π )
θ 6 θ 5 = 3 π 8 ± ( p π )

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