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Spectral slicing of broadband light has been proposed as a means to enable cost- effective, high-speed wavelength division multiplexed (WDM) passive optical networks (PON). In this section, we present an all-fiber based approach for generating comb-like- spectrum light for WDM-PON application.

Figure 10 Spectral slicing of broadband light has been proposed as a means to enable cost- effective, high-speed wavelength division multiplexed (WDM) passive optical networks (PON). In this section, we present an all-fiber based approach for generating comb-like- spectrum light for WDM-PON application.

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Fig.1. Optical spectra of the output of the fiber ring laser using nonlinear fibers with three different dispersions at 1550nm (D=-1.4, 0.196, 14.673 ps/nm/km). rates through modulation instability effect in the anomalous dispersion fiber. At higher powers, the SC is generated mostly by stimulated Raman scattering (SRS) and intra-pulse SRS effects.
Fig.1. Optical spectra of the output of the fiber ring laser using nonlinear fibers with three different dispersions at 1550nm (D=-1.4, 0.196, 14.673 ps/nm/km). rates through modulation instability effect in the anomalous dispersion fiber. At higher powers, the SC is generated mostly by stimulated Raman scattering (SRS) and intra-pulse SRS effects.
Fig.2. Optical spectrum of input ASE pump and the spectra of the output from DSF1, DSF2, and DSF3. To demonstrate the proposed idea we conducted an experiment using a high power EDFA as a pump ASE source and three pieces of DSF with zero dispersion in the 1550 nm range as a nonlinear medium. The EDFA delivers a maximum output ASE power up to 2W. The zero dispersion wavelengths of DSF1, DSF2, and DSF3 are at ~1531, ~1550, and ~1590 nm, respectively. The lengths of the DSF1, DSF2, and DSF3 are lkm, lkm, and 4km, respectively.
Fig.2. Optical spectrum of input ASE pump and the spectra of the output from DSF1, DSF2, and DSF3. To demonstrate the proposed idea we conducted an experiment using a high power EDFA as a pump ASE source and three pieces of DSF with zero dispersion in the 1550 nm range as a nonlinear medium. The EDFA delivers a maximum output ASE power up to 2W. The zero dispersion wavelengths of DSF1, DSF2, and DSF3 are at ~1531, ~1550, and ~1590 nm, respectively. The lengths of the DSF1, DSF2, and DSF3 are lkm, lkm, and 4km, respectively.
Fig.4. Supercontinuum width of the output from DSF2 Fig.3. Evolution of the spectrum of the output from DSF2 with pump power. Fig. 2 shows the measured input ASE spectrum and the output spectra after DSF1, DSF2, and DSF3 for the input pump power of 1.5 W. The peak of the input ASE spectrum is at ~1535 nm which nearly coincides with the zero dispersion of the DSF1. The -15dB spectral width is ~15 nm. After DSF1 the spectrum is broadened to 90 nm (at -15dB level) due to four-wave mixing in the fiber and the peak of the spectrum is shifted to ~1550 nm because of the SRS effect. Since the dispersion zero of the DSF2 is at the spectral peak of the output of the DSF1, the four-wave mixing in the DSF2 further enlarges the spectral bandwidth to ~ 200 nm (at -15dB level). Again the SRS effect shifts the spectral peak of the output from DSF2 to ~1573nm. Finally, a 240 nm (at -15dB level) broad SC is produced at the output of DSF3. Figure 3 illustrates the evolution of the SC spectrum at the output from DSF2 with the pump power and Fig. 4 plots the change of the SC spectral bandwidth of the output from DSF2 at -5, -10, and -15dB level versus the output power. At the maximum launched pump power level of 1.96 W, the SC spectrum of the output of DSF2 extends over 268 nm at -15dB level, and the output power reaches 0.73 W, giving an average spectral power density of 2.7 mW/nm.
Fig.4. Supercontinuum width of the output from DSF2 Fig.3. Evolution of the spectrum of the output from DSF2 with pump power. Fig. 2 shows the measured input ASE spectrum and the output spectra after DSF1, DSF2, and DSF3 for the input pump power of 1.5 W. The peak of the input ASE spectrum is at ~1535 nm which nearly coincides with the zero dispersion of the DSF1. The -15dB spectral width is ~15 nm. After DSF1 the spectrum is broadened to 90 nm (at -15dB level) due to four-wave mixing in the fiber and the peak of the spectrum is shifted to ~1550 nm because of the SRS effect. Since the dispersion zero of the DSF2 is at the spectral peak of the output of the DSF1, the four-wave mixing in the DSF2 further enlarges the spectral bandwidth to ~ 200 nm (at -15dB level). Again the SRS effect shifts the spectral peak of the output from DSF2 to ~1573nm. Finally, a 240 nm (at -15dB level) broad SC is produced at the output of DSF3. Figure 3 illustrates the evolution of the SC spectrum at the output from DSF2 with the pump power and Fig. 4 plots the change of the SC spectral bandwidth of the output from DSF2 at -5, -10, and -15dB level versus the output power. At the maximum launched pump power level of 1.96 W, the SC spectrum of the output of DSF2 extends over 268 nm at -15dB level, and the output power reaches 0.73 W, giving an average spectral power density of 2.7 mW/nm.
Fig.5. Standard deviation of the power across the entire wavelength range of the SC over a period of 100 minutes. Fig.6. Spectra of the SC output with Raman pump (solid line) and without Raman pump (dash line). We investigated the long-term stability of the SC spectrum at the output from DSF2 at a fixed pump power of 1.88 W over a period of 100 minutes. Spectra of the SC were acquired at a regular time interval of 5 minutes. The maximum power fluctuation of the input over that time period was 2%. Fig.5 shows the standard deviation of the power across the entire wavelength range of the SC over a period of 100 minutes. The SC spectrum exhibits good long-term stability with a maximum standard deviation in power of only 0.09 dB over a period of 100 minutes.
Fig.5. Standard deviation of the power across the entire wavelength range of the SC over a period of 100 minutes. Fig.6. Spectra of the SC output with Raman pump (solid line) and without Raman pump (dash line). We investigated the long-term stability of the SC spectrum at the output from DSF2 at a fixed pump power of 1.88 W over a period of 100 minutes. Spectra of the SC were acquired at a regular time interval of 5 minutes. The maximum power fluctuation of the input over that time period was 2%. Fig.5 shows the standard deviation of the power across the entire wavelength range of the SC over a period of 100 minutes. The SC spectrum exhibits good long-term stability with a maximum standard deviation in power of only 0.09 dB over a period of 100 minutes.
Table 1: Comparison of RIN values for 1-nm spectral slices before and after the entering the RSOA
Table 1: Comparison of RIN values for 1-nm spectral slices before and after the entering the RSOA
Fig.7. Transmission system comprised of SC source, 20 km of single-mode fiber, 1 nm tunable filter, reflective SOA modulator, and BERT equipment. tunable filter. Our CW-SC-ASE source produces an additional 3 dB/Hz of noise power in comparison with the ASE of an EDFA; however it is capable of producing bandwidths up to 268nm (at -15dB level) with an average spectral density of 2.7mW/nm[10]. Despite the seemingly high RIN values, the use of a saturated semiconductor optical amplifier (SOA), typically utilized in ASE-based WDM-PONs, allows to suppress the noise power by approximately 13 dB at 1.25 GHz[8-14]. This is depicted in Table 1 where the RIN power at 1.25 GHz was measured after retro-reflecting in the RSOA. While simultaneously suppressing the noise of the input, the RSOA retro-reflected a 1.25 Gb/s signal back through the transmission fiber where it was measured at port ‘3’ of the optical circulator using a commercial GBIC receiver and BER test equipment. The results of this transmission are shown in Fig.8; the data indicates a 10° receiver sensitivity of about -24.5 dBm across three sampled wavelengths of the SC spectrum with a 1.9 dB dispersion power penalty for the 1-nm spectral slice at the longest sampled 1565 nm. Here the operation bandwidth was limited by the range of the tunable filter, but this wavelength is otherwise inaccessible if the ASE spectrum from an EDFA was used to feed the RSOA.
Fig.7. Transmission system comprised of SC source, 20 km of single-mode fiber, 1 nm tunable filter, reflective SOA modulator, and BERT equipment. tunable filter. Our CW-SC-ASE source produces an additional 3 dB/Hz of noise power in comparison with the ASE of an EDFA; however it is capable of producing bandwidths up to 268nm (at -15dB level) with an average spectral density of 2.7mW/nm[10]. Despite the seemingly high RIN values, the use of a saturated semiconductor optical amplifier (SOA), typically utilized in ASE-based WDM-PONs, allows to suppress the noise power by approximately 13 dB at 1.25 GHz[8-14]. This is depicted in Table 1 where the RIN power at 1.25 GHz was measured after retro-reflecting in the RSOA. While simultaneously suppressing the noise of the input, the RSOA retro-reflected a 1.25 Gb/s signal back through the transmission fiber where it was measured at port ‘3’ of the optical circulator using a commercial GBIC receiver and BER test equipment. The results of this transmission are shown in Fig.8; the data indicates a 10° receiver sensitivity of about -24.5 dBm across three sampled wavelengths of the SC spectrum with a 1.9 dB dispersion power penalty for the 1-nm spectral slice at the longest sampled 1565 nm. Here the operation bandwidth was limited by the range of the tunable filter, but this wavelength is otherwise inaccessible if the ASE spectrum from an EDFA was used to feed the RSOA.
Fig.8. Measured BER curves using CW-SC source and the RSOA in a WDM-PON configuration IV. Supercontinuum generation in optical fibers pumped by fs pulses. al ball Dispersion management along fiber in SC generation in optical fibers is investigated in this section by using fs optical pulses. The unique features of our approach are 1) the system is all-fiber based and 2) conventional nonlinear fiber is used. Fig.9 shows the experimental setup. The oscillator was a stretched-pulse mode-locked fiber laser using nonlinear polarization rotation which could generate 91 fs optical pulses with a repetition rate of 31.1 MHz. The output pulses from the oscillator were first amplified by a high-power EDFA, then sent to a 7.7 m piece of standard SMF, and finally launched into a 1 km nonlinear DSF with a zero dispersion at around 1552nm. The nonlinear coefficient of the DSF is about 17 W'km".
Fig.8. Measured BER curves using CW-SC source and the RSOA in a WDM-PON configuration IV. Supercontinuum generation in optical fibers pumped by fs pulses. al ball Dispersion management along fiber in SC generation in optical fibers is investigated in this section by using fs optical pulses. The unique features of our approach are 1) the system is all-fiber based and 2) conventional nonlinear fiber is used. Fig.9 shows the experimental setup. The oscillator was a stretched-pulse mode-locked fiber laser using nonlinear polarization rotation which could generate 91 fs optical pulses with a repetition rate of 31.1 MHz. The output pulses from the oscillator were first amplified by a high-power EDFA, then sent to a 7.7 m piece of standard SMF, and finally launched into a 1 km nonlinear DSF with a zero dispersion at around 1552nm. The nonlinear coefficient of the DSF is about 17 W'km".
Fig.10. (1) Optical spectrum measured from the output of the fiber laser. (2) Optical spectrum measured after the SMF. (3) Optical spectrum measured from the output of the DSF.
Fig.10. (1) Optical spectrum measured from the output of the fiber laser. (2) Optical spectrum measured after the SMF. (3) Optical spectrum measured from the output of the DSF.
Fig.12. Optical spectrum of the output pulses from | km nonlinear DSF. eye diagram of the reflected light from the SOA for a bit rate of 622Mb/s. The eye is clear and wide open, indicating that this approach is realizable.
Fig.12. Optical spectrum of the output pulses from | km nonlinear DSF. eye diagram of the reflected light from the SOA for a bit rate of 622Mb/s. The eye is clear and wide open, indicating that this approach is realizable.
Fig.13. Eye diagram of the reflective light from the SOA. VI. Conclusions
Fig.13. Eye diagram of the reflective light from the SOA. VI. Conclusions
Related topics:
Fiber LasersFiber LaserAmplified spontaneous emissionPulse CompressionWavelength Division MultiplexingOptical FibersAccess Network
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