No abstract

An all-optical clock recovery module is developed and tested in a 100 Gbit/s 105 km transmission experiment. A penalty free function of the optical clock relative to an electronic phase-locked loop is demonstrated. The compact module is wavelength and polarisation insensitive and requires no electrical radiofrequency equipment. Continuous frequency tuning from 5 to 22 GHz indicates the potential for bit rate flexible clock recovery

A theoretical model of a self-pulsating three-section DFB laser with an integrated phase tuning section is established. Parameters of an existing device are used for applying the model. Key conditions and characteristics of a self-pulsations (SP) are modeled and compared with experimental results. The important role of phase tuning for turning on the SP is pointed out. The dependece of the SP regime on the detuning between the Bragg wavelengths in the laser and reflector is determind and the essential role of phase-readjustment is identified. Frequency tuning via the laser currents, as well as the pulse shape at various frequencies, is investigated. This allows us to identify the mechanism for frequency tuning. The model turns out to be a good tool to improve our knowledge of the self-pulsation effect and to design optimized devices

In coherent optical systems or sensors, polarization matching between the superposed beams must be assured. The tracking range of automatic polarization control systems should be endless, i.e., any resets of finite range retarders, which transform the polarization, should cause no significant intensity losses. A variety of experimental systems including a computer as feedback controller are described in this paper. They include the minimum configuration of three fixed eigenmode retarders. i.e., the orientation of birefringence cannot be changed. These retarders are realized by fiber squeezers. Errortolerant systems which contain more than the minimum number of elements, however, are better suited to cope with time variant retarder transfer functions, etc. A fourth Rber squeezer allows the losses of a nonideal system to be kept to only 0.07 dB. Finally for the first time a closed loop system with two integrated optical retarders is described. These retarders have variable eigenmodes, i.e., adjustable birefringence orientation. An optimization procedure helps to idealize the device behavior. The system has less than 0.15 dB intensity losses, coupling and attenuation not Included.

In a monolithic heterodyne polarization diversity receiver, mode splitters which effectively separate the TE and TM polarization of the optical wave are required. For this purpose, a directional coupler which utilizes a metal cladding on one of its branches to separate both polarizations was investigated. The polarization splitters can act in two distinct modes of operation, depending on the degree of lateral confinement of the optical rib waveguide before an asymmetric coupler. For weak confinement, the metallized waveguide is guiding for TE- but nonguiding for TM-polarization, and negligible TM-crosstalk results

In this work, the influence of ammonium sulfide (NH 4 ) 2 S passivation on waveguide based mid-infrared InAs/GaSb superlattice photodetectors (2-5 μm wavelength) has been studied. The current-voltage characteristics for reverse as well as for forward bias of passivated samples have been examined. The advantages of this have been the reduction of the reverse leakage current and the increase of zero bias resistance. As a disadvantage the decrease of the photoresponsivity after sulfur passivation has been found. Furthermore, it has been observed that the passivation solution does not only passivate the surface of GaSb, but it also reacts with entire GaSb layers and can destroy the devices.

No abstract

No abstract