Abstract

A linearized dual parallel Mach-Zehnder modulator (DPMZM) based on electro-optic (EO) polymer was both fabricated, and experimentally used to suppress the third-order intermodulation distortion (IMD3) in a coherent analog fiber optic link. This optical transmitter design was based on a new EO chromophore called B10, which was synthesized for applications dealing with the fiber-optic communication systems. The chromophore was mixed with amorphous polycarbonate (APC) to form the waveguide’s core material. The DPMZM was configured with two MZMs, of different lengths in parallel, with unbalanced input and output couplers and a phase shifter in one arm. In this configuration each of the MZMs carried a different optical power, and imposed a different depth of optical modulation. When the two optical beams from the MZMs were combined to generate the transmitted signal it was possible to set the IMD3 produced by each modulator to be equal in amplitude but 180° out of phase from the other. Therefore, the resulting IMD3 of the DPMZM transmitter was effectively canceled out during two-tone experiments. A reduction of the IMD3 below the noise floor was observed while leaving fifth-order distortion (IMD5) as the dominant IMD product. This configuration has the capability of broadband operation and shot-noise limited operation simultaneously.

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  1. B. M. Haas and T. E. Murphy, “A simple, linearized, phase-modulated analog optical transmission system,” IEEE Photon. Technol. Lett. 19(10), 729–731 (2007).
    [CrossRef]
  2. A. Djupsjobacka, “A linearization concept for integrated-optic modulators,” IEEE Photon. Technol. Lett. 4(8), 869–872 (1992).
    [CrossRef]
  3. S. K. Korotky and R. M. de Ridder, “Dual parallel modulation schemes for low-distortion analog optical transmission,” IEEE J. Sel. Areas Comm. 8(7), 1377–1381 (1990).
    [CrossRef]
  4. G. Zhu, W. Liu, and H. R. Fetterman, “A broadband linearized coherent analog fiber optic link employing dual parallel mach-zehnder modulators,” IEEE Photon. Technol. Lett. 21(21), 1627–1629 (2009).
    [CrossRef]
  5. H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
    [CrossRef]
  6. W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
    [CrossRef]
  7. B. Li, R. Dinu, D. Jin, D. Huang, B. Chen, A. Barklund, E. Miller, M. Moolayil, G. Yu, Y. Fang, L. Zheng, H. Chen, and J. Vemagiri, “Recent advances in commercial electro-optic polymer modulator,” OFC/OC 2007, 115–117 (2007).
  8. S. Kim, W. Lui, Q. Pei, L. R. Dalton, and H. R. Fetterman, “Suppression of intermodulation distortion in coherent system using polymeric dual parallel Mach Zehnder Modulators,” in Conference on CLEO/QELS 2010, Technical paper ATuB2 (2010).

2009 (1)

G. Zhu, W. Liu, and H. R. Fetterman, “A broadband linearized coherent analog fiber optic link employing dual parallel mach-zehnder modulators,” IEEE Photon. Technol. Lett. 21(21), 1627–1629 (2009).
[CrossRef]

2007 (2)

B. M. Haas and T. E. Murphy, “A simple, linearized, phase-modulated analog optical transmission system,” IEEE Photon. Technol. Lett. 19(10), 729–731 (2007).
[CrossRef]

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

2003 (1)

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

1992 (1)

A. Djupsjobacka, “A linearization concept for integrated-optic modulators,” IEEE Photon. Technol. Lett. 4(8), 869–872 (1992).
[CrossRef]

1990 (1)

S. K. Korotky and R. M. de Ridder, “Dual parallel modulation schemes for low-distortion analog optical transmission,” IEEE J. Sel. Areas Comm. 8(7), 1377–1381 (1990).
[CrossRef]

Chang, D. H.

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

de Ridder, R. M.

S. K. Korotky and R. M. de Ridder, “Dual parallel modulation schemes for low-distortion analog optical transmission,” IEEE J. Sel. Areas Comm. 8(7), 1377–1381 (1990).
[CrossRef]

Dinu, R.

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

Djupsjobacka, A.

A. Djupsjobacka, “A linearization concept for integrated-optic modulators,” IEEE Photon. Technol. Lett. 4(8), 869–872 (1992).
[CrossRef]

Fetterman, H. R.

G. Zhu, W. Liu, and H. R. Fetterman, “A broadband linearized coherent analog fiber optic link employing dual parallel mach-zehnder modulators,” IEEE Photon. Technol. Lett. 21(21), 1627–1629 (2009).
[CrossRef]

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

Haas, B. M.

B. M. Haas and T. E. Murphy, “A simple, linearized, phase-modulated analog optical transmission system,” IEEE Photon. Technol. Lett. 19(10), 729–731 (2007).
[CrossRef]

Jin, D.

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

Kim, S.

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

Korotky, S. K.

S. K. Korotky and R. M. de Ridder, “Dual parallel modulation schemes for low-distortion analog optical transmission,” IEEE J. Sel. Areas Comm. 8(7), 1377–1381 (1990).
[CrossRef]

Liu, W.

G. Zhu, W. Liu, and H. R. Fetterman, “A broadband linearized coherent analog fiber optic link employing dual parallel mach-zehnder modulators,” IEEE Photon. Technol. Lett. 21(21), 1627–1629 (2009).
[CrossRef]

Murphy, T. E.

B. M. Haas and T. E. Murphy, “A simple, linearized, phase-modulated analog optical transmission system,” IEEE Photon. Technol. Lett. 19(10), 729–731 (2007).
[CrossRef]

Seong-Ku Kim, H.

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

Steier, W. H.

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

Wang, C.

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

Yuan, W.

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

Zhang, C.

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

Zhang, H.

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

Zhu, G.

G. Zhu, W. Liu, and H. R. Fetterman, “A broadband linearized coherent analog fiber optic link employing dual parallel mach-zehnder modulators,” IEEE Photon. Technol. Lett. 21(21), 1627–1629 (2009).
[CrossRef]

IEEE J. Sel. Areas Comm. (1)

S. K. Korotky and R. M. de Ridder, “Dual parallel modulation schemes for low-distortion analog optical transmission,” IEEE J. Sel. Areas Comm. 8(7), 1377–1381 (1990).
[CrossRef]

IEEE Photon. Technol. Lett. (5)

G. Zhu, W. Liu, and H. R. Fetterman, “A broadband linearized coherent analog fiber optic link employing dual parallel mach-zehnder modulators,” IEEE Photon. Technol. Lett. 21(21), 1627–1629 (2009).
[CrossRef]

H. Seong-Ku Kim, H. Zhang, D. H. Chang, C. Zhang, C. Wang, W. H. Steier, and H. R. Fetterman, “Electrooptic polymer modulators with an inverted-rib waveguide structure,” IEEE Photon. Technol. Lett. 15(2), 218–220 (2003).
[CrossRef]

W. Yuan, S. Kim, H. R. Fetterman, W. H. Steier, D. Jin, and R. Dinu, “Hybrid integrated cascaded 2-bit electrooptic digital optical switches (DOSs),” IEEE Photon. Technol. Lett. 19(7), 519–521 (2007).
[CrossRef]

B. M. Haas and T. E. Murphy, “A simple, linearized, phase-modulated analog optical transmission system,” IEEE Photon. Technol. Lett. 19(10), 729–731 (2007).
[CrossRef]

A. Djupsjobacka, “A linearization concept for integrated-optic modulators,” IEEE Photon. Technol. Lett. 4(8), 869–872 (1992).
[CrossRef]

Other (2)

B. Li, R. Dinu, D. Jin, D. Huang, B. Chen, A. Barklund, E. Miller, M. Moolayil, G. Yu, Y. Fang, L. Zheng, H. Chen, and J. Vemagiri, “Recent advances in commercial electro-optic polymer modulator,” OFC/OC 2007, 115–117 (2007).

S. Kim, W. Lui, Q. Pei, L. R. Dalton, and H. R. Fetterman, “Suppression of intermodulation distortion in coherent system using polymeric dual parallel Mach Zehnder Modulators,” in Conference on CLEO/QELS 2010, Technical paper ATuB2 (2010).

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Figures (7)

Fig. 1
Fig. 1

EO material and device structure. (a) chemical structure of guest material, B10LC103 (or B10), (b) device cross-section, and (c) material properties of B10-APC.

Fig. 2
Fig. 2

Schematic diagram of the device fabrication process. A thin layer of a protection layer made of a diluted APC in TCE solution was applied to prevent from unwanted dielectric breakdown during the poling procedure. The electrode contact poling process (a circle) was done in a lab-made nitrogen purged box. The slab height of each layer such as lower cladding, core layer, and upper cladding was measured to be 2.5 μm thick, respectively. Different waveguide widths was chosen to be 3, 3.5, and 4 μm wide.

Fig. 3
Fig. 3

Half-wave voltage measurements of all the components that used to construct a DPMZM transmitter (as shown in Fig. 4 and 5). Each component was diced from the same internal chip. (a) a Mach-Zehnder modulator 1 (MZ1), Vπ = 3V with an interaction length of 2cm, (b) MZ2, Vπ = 2V with an interaction length of 2.5cm, (c) a directional coupler modulator, Vπ = 4.31V with an interaction length of 1.5cm, and (d) a phase shifter, Vπ = 10.5V with an interaction length of 0.5cm. The device measurements were performed at a low-frequency of 1KHz.

Fig. 4
Fig. 4

Schematic layout of (a) a linearized DPMZM transmitter, and (b) a test setup. It includes a DPMZM transmitter, the laser source of 1550nm, the erbium-doped fiber amplifier (EDFA), the local oscillator (LO), and the optical filter (FBG). The LO is generated using an optical modulator, operating at 12.25278 GHz along with an optical filter (FBG) to separate the sideband. The EDFA was used to develop sufficient optical power. Polarization controllers are utilized before and after the DPMZM and the LO. The LO is used to beat the generated DSSC signal to an IF frequency (7.25278GHz). To achieve the maximum beating current, the LO has been appropriately tuned, and the beating is done using a 3 dB coupler followed by an amplifier and either a photodetector or balanced photodetector for RIN suppression.

Fig. 5
Fig. 5

Photograph of the polymeric DPMZM optical transmitter. The DPMZM is fiber-aligned in both sides, and the two MZM electrodes are contacted with GSG probes, respectively. For electrical contacts for the directional coupler, the phase shifter, and the ground contact, low-frequency pico-probes were utilized.

Fig. 6
Fig. 6

Experimental results for two-tone IMD test. (a) without and (b) with linearization. The IMD3 was suppressed by >30dB to the noise level, while the fundamental power was sacrificed by ~10dB. The improved linearity was achieved at the expense of a small decrease in the fundamental amplitude signal due to a partial cancellation when the dominant distortion from the MZMs is subtracted [3].

Fig. 7
Fig. 7

Output power versus input RF power from the two-tone RF spectrum. (▪) with slope = 1 represents the fundamental signal without linearization, and (●) with slope = 3 represents the third order intermodulation distortion without linearization, (▲) with slope = 1 and (▼) with slope = 5 are the fundamental and IMD5 signal after linearization process. It is note that the suppression of IMD3 has not been optimized with β to obtain maximum distortion suppression. However, the SFDR enhancement of ~7dB in above experiment was determined.

Equations (2)

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A o u t = A i n cos α cos β sin m 2 A i n sin α sin β sin γ 1 m 2
tan α tan β = γ 3

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