B. C. Barnett

Cascadability and functionality of all-optical low-birefringent nonlinear optical loop mirror: experimental demonstration

We verify both experimentally and theoretically the cascadability and the Boolean complete functionality of the low-birefringent nonlinear optical loop mirror (low-bi NOLM) operating with all inputs at the same wavelength. We achieve a low switching energy by using a low-birefringent (Δn∼3.5×10-6), polarization-maintaining fiber to achieve a longer interaction length between two orthogonally polarized pulses. We experimentally demonstrate switching in the cascaded operation of two low-bi NOLMs using picosecond pulses from an erbium-doped fiber laser. This has the potential to have a bit rate of 100 Gb/s. After the two cascaded low-bi NOLMs, the performance is a peak switching contrast of 36:1 and a timing window of 1.7 pulse widths with a switching energy of 9 pJ. In addition, we demonstrate the and and the xor/not operations with the low-bi NOLM showing Boolean completeness. The and operation has a switching contrast of 84.5:1, and the xor/not has a switching contrast of 11.5:1. Finally, we study the gate numerically and find good agreement between experiments and simulations.

Soliton logic gate using low-birefringence fiber in a nonlinear loop mirror

We demonstrate, using numerical simulations, a new all-optical logic gate that combines the mechanisms of soliton dragging and nonlinear-optical loop mirrors (NOLM’s). The design uses specially wrapped low-birefringence polarization-maintaining fiber, which we recently demonstrated in the NOLM configuration. Combining the soliton dragging and NOLM effects increases the timing window of the gate, and using the low-birefringence fiber minimizes the number of cross splices required. For example, we show that by using only one cross splice we can achieve a switching energy of 5.3 pJ and a total timing window of 3.3 pulse widths. We also present a set of design rules for our low-birefringence NOLM.

Synchronization of two passively mode-locked erbium-doped fiber lasers by an acousto-optic modulator and grating scheme.

We synchronize two passively mode-locked erbium-doped fiber lasers by adjusting only the cavity length to correct both the repetition rate and the phase. The interlaser jitter is less than 6 ps (1.3 times the pulse width) and is extracted from the cross correlation of the two lasers. The lock can be maintained for extended periods of time. These results are obtained by use of a novel acousto-optic-modulator-grating scheme, which provides an equivalent of 300 microm in cavity length tuning with a bandwidth of 10 kHz. These parameters are 30 times the length and 10 times the bandwidth of a typical piezoelectric transducer.

Experimental cascaded operation of low-birefringence nonlinear-optical loop mirrors

We experimentally demonstrate the operation of a low-birefringence (low-bi) nonlinear-optical loop mirror (NOLM) that has the advantages of low switching energy, tolerance to timing jitter, and cascadability. Because cascading two all-optical logic gates is an important step toward high-speed optical signal processing and header processing in time-division-multiplexed networks, we also demonstrate the cascaded operation of two low-bi NOLMs. Using a passively mode-locked fiber laser that produces 450-fs pulses at a wavelength of 1.55 microm, we achieve a 10.7:1 switching contrast ratio and a 2.7-pulse-widths-wide timing window after the cascaded gates. The results agree well with theoretical predictions and confirm the advantages of the long interaction length associated with orthogonally polarized pulses in low-bi (Deltan ~ 3.0 x 10(-6)) polarization-maintaining fiber.

Experimental demonstration of a low-latency fiber soliton logic gate

We experimentally demonstrate switching in a 50 m-long soliton logic gate with a switching energy of 40 pJ using 490 fs pulses at 1.553 /spl mu/m from an erbium-doped fiber laser. A full characterization of this gate shows a peak contrast ratio of 4.2:1, a timing window of 1.1 pulse width and cascadable operation. To our knowledge, the gate length of 50 m is at least six times shorter than other designs with comparable switching energies. The low-latency of this gate is possible due to a low-birefringent polarization-maintaining fiber that possesses a high polarization extinction ratio of up to 20 dB with a low birefringence of 2.6/spl times/10/sup -6/. The low birefringence leads to a longer walk-off length between two orthogonally polarized pulses, where the walk-off length for 490 fs pulses is 56 m. We also study this gate numerically and find good agreement between the simulations and experiments.

High-speed header processing using synchronized fiber lasers driving all-optic logic gates

We show all-optic logic gates driven by synchronized erbium-doped fiber lasers (EDFLs) to perform 100 Gb/s header processing in TDM packetized networks or optical add/drop multiplexers. We experimentally demonstrate AND and XOR logic functions in low-birefringent nonlinear optical loop mirrors (Low-Bi-NOLMs) with switching energy as low as 9 pJ and peak switching contrast of 8:1. We show that the Low-Bi-NOLMs satisfy decision-making capabilities in a header processor such as cascadability and Boolean-complete logic functions. Our novel AOM-grating scheme of synchronization provides 30 times the length and 10 times the bandwidth as compared to the scheme using piezo-electric transducers (PZTs). We have achieved synchronization of two passively mode-locked EDFLs with a timing jitter of approximately 1.3 times the pulse width. We are now integrating the synchronized EDFLs and all-optic logic gates, which are key components for packet addressing for 100 Gb/s applications.