摘要:
Disclosed is a time division multiplexed optical communication system that is capable of operation at relatively high bit rates and that is relatively stable and immune to crosstalk and noise. The system comprises receiver means wherein the timing signal for demultiplexing is derived from the fully multiplexed optical pulse stream by means that comprise a narrow band receiver and timing means that produce a lower-frequency timing signal from the output of the narrow band receiver. The timing signal is used to drive one or more optical switches. In one embodiment of the invention the receiver means have a binary-tree architecture and the timing signals are substantially sinusoidal. In another embodiment the receiver means have a linear-bus architecture and the timing signals are pulse-like.
摘要:
Optical functions such as Q-switching, mode locking, cavity dumping, and modulation are generated by a simple laser arrangement which includes a gain medium and an electrically controllable, optical waveguide device optically coupled to the gain medium. The gain medium and waveguide device are either interposed between two reflective surfaces or coupled by a waveguide in order to form a single composite cavity laser structure.
摘要:
Optical functions such as Q-switching, mode locking, cavity dumping, and modulation are generated by a simple laser arrangement which includes a gain medium and an electrically controllable, optical waveguide device optically coupled to the gain medium. The gain medium and waveguide device are either interposed between two reflective surfaces or coupled by a waveguide in order to form a single composite cavity laser structure. -
摘要:
Wavelength tunability and single frequency output are achieved in a coherent light source employing an adjustably controllable reflector. The light source includes a gain medium coupled to a single-mode fiber having a partially reduced cladding region at a predetermined distance from the gain medium. A Bragg reflector is either formed on the reduced cladding region of the single-mode fiber or formed on an external element in close proximity to the reduced cladding region. A single resonant optical cavity is formed by placing another reflector on the side of the gain medium opposite the gain medium-to-fiber coupling. Wavelength tuning of the light source is accomplished by controllably adjusting the period or the Bragg reflector element.
摘要:
Prior art techniques for velocity matching the optical wave and the modulating electrical wave in traveling wave, electrooptic devices includes the use of phase reversals and intermittent interaction. This results in a device whose frequency response includes a single peak. It has been discovered that by reducing the length of the interaction intervals between the electrical and optical systems, a multiplicity of harmonically related frequency peaks can be obtained. Furthermore, by combining the phase reversal and intermittent interaction techniques in a common device, the available bandwidth can be doubled.
摘要:
A double-periodic grating is described for obtaining polarization-independent filtering and coupling. The grating may be viewed as a combination of two gratings with slightly different grating periods. The two periods are carefully chosen to match the difference in propagation constants of the TE and TM polarization modes such that both modes are coupled at the same wavelength.A novel method of obtaining a double-periodic grating is described.
摘要:
A grating coupler is combined with a quantum well index modulator and an optical waveguide to alter the reverse or forward coupling characteristics between two different propagation modes of the system.
摘要:
An optical filter using first and second grating sections separated by a changed refractive index section operates as a narrowband grating resonator.
摘要:
Tunable, polarization independent wavelength filtering is obtained in a circuit configuration comprising an input polarization selective coupler which separates the TM and TE mode waves. A first, wavelength selective mode converter, in the TE mode wavepath, converts the TE mode wave energy at the selected wavelength to the TM mode. Similarly, a second wavelength selective mode converter, located in the TM mode wavepath, converts the TM mode wave energy at the selected wavelength to the TE mode. An output polarization selective coupler combines the TE and TM mode wave energy at the selected wavelength in one output wavepath and combines the balance of the input signal in a second wavepath. By cascading a plurality of such circuits, each tuned to a different wavelength, a wavelength multiplexed signal can be demultiplexed.
摘要:
The coupling efficiency between a pair of identical optical waveguides (11, 12) is modulated by a traveling electrical wave (14, 15). Because the propagating constants of the optical and modulating systems are not equal, the interaction between them is limited to periodic intervals along the optical wavepaths. By the appropriate selection of this spatial period, a velocity match between the modulating and optical systems is simulated.