A computational model of the bottlenose dolphin sonar: Feature-extracting method
A process of echo‐image formation in bottlenose dolphin perception was investigated in our experiments, in which animals were trained to differentiate passive actual echoes recorded beforehand purposely, as well as echo‐like simulated impulses. The results suggest that dolphin, processing echoes within critical interval of time (∼0.2 ms), utilizes the string of three independent, hierarchically organized features (echoes subjective characteristics) being defined by different scales of spectral density oscillation, and energy. Herewith, dolphin is capable to assess features average value over a series of echoes. Distinguishing stimuli, dolphin estimates successively features values from senior to minor, terminating the process at the feature, which contains detectable differences in compared stimuli (the distinctive feature). A procedure of subsequent identification of the reference stimulus can be described by the following decision rule: If the dolphin utilizes some feature as the distinctive one, then i...
Representation and processing of acoustic information in a biomimetic neural network
Abstract : The effectiveness of artificial neural network models depends strongly on the way in which the information to be learned is presented to the network. Use of biologically relevant mechanisms is likely to yield effective syntactic systems as well as understanding the performance of biological systems. We developed a model of the dolphin cochlea and used this model to produce the representations used by a neural network to model the delayed matching-to-sample performance of a bottlenosed dolphin. The model yielded psychophysical functions and matching choice accuracy similar to those obtained from the dolphin.... Artificial neural networks (AN-N), Echolocation Gateway- integrator neural network (GIN)
Design and Fabrication of Wide Wavelength Range 25.8-Gb/S, 1.3-μM, Push-Pull-Driven DMLs
We design and fabricate wide wavelength range directly modulated lasers (DMLs) on the same InP wafer to realize a large-capacity monolithically integrated light source array up to 1 Tb/s. We demonstrate a 25.8-Gb/s push-pull operation over a 30-nm wavelength range, which is conventionally about 14 nm for 100 GbE applications. To extend the operating wavelength range, we design the wavelength dependence of the differential gain (∂G/∂n) for an InGaAlAs multiple quantum well structure, and realize high frequency relaxation oscillation resulting from the high differential gain over a wide range. Next, we also design the wavelength detuning (Δλ) under an operating injection current condition by taking account of the thermal effect of the chip, because Δλ determines ∂G/∂n, and the threshold current of the laser diode (LD). In addition, to achieve a 25.8-Gb/s push-pull operation, we fabricate a ridge waveguide structure buried in benzocyclobutene (BCB) with a low parasitic capacitance, and electrically isolate the DML from the neighboring chip by etching off n-InP. By using this design and structure, we achieve a 3-dB-down frequency bandwidth of over 20 GHz from 1290 to 1320 nm. We also achieve a mean output power of 8.0 dBm, and a dynamic extinction ratio of 5 dB. We measure the 25.8-Gb/s transmission characteristics, and obtain clear eye openings for a back-to-back configuration. We also measure the bit-error-rate performance, and obtain error-free operation for a 30-nm operating wavelength range.