Abstract: The present disclosure describes an apparatus and system that includes a diffractive optical lens. The diffractive optical lens includes a central region shaped as a convex lens, an intermediate region laterally surrounding the central region and composed of multiple concentric zones, and an outer region laterally surrounding the intermediate region. A respective outer radius rh of each of the concentric zones in the intermediate region is (Eq. 1), where ?0 is an operating wavelength of the diffractive optical lens, f is a focal length of the diffractive optical lens, and h is an integer. At least one of the zones in the intermediate region includes at least one of (i) a continuous annular trough or (ii) a plurality of isolated holes that collectively encircle the central region.

Abstract: A switching node in a distributed transmission network. The node, which is assigned a unique switching node identity (SID) includes a number of switch ports for connection of a number of line boards with subscriber line ports. The node detects a request for an IP address from a line board and identifies the switch port on which the request is received. The node generates an extended IP address request message by adding information about the SID and the receiving switch port over which the IP address request was received. The node forwards the extended IP address request message to a control unit within the node or to an external switching control node.

Abstract: The invention relates to fabrication of VCSELs. It provides a method for fabricating a VCSEL that contains a micro/nano-structured mode selective lateral layer, where the micro/nano-structured layer is obtained by well controlled local etching. The invention enables control of the micro/nano-structured layer thickness with very high precision. In particular, the invention relates to a method for fabricating a VCSEL with a micro/nano-structured mode selective layer for controlling the VCSELs transverse electromagnetic modes.

Abstract: A switching node in a distributed transmission network. The node, which is assigned a unique switching node identity (SID) includes a number of switch ports for connection of a number of line boards with subscriber line ports. The node detects a request for an IP address from a line board and identifies the switch port on which the request is received. The node generates an extended IP address request message by adding information about the SID and the receiving switch port over which the IP address request was received. The node forwards the extended IP address request message to a control unit within the node or to an external switching control node.

Abstract: This specification discloses a VCSEL (Vertical-Cavity Surface-Emitting Laser) device with single-mode output and optionally single polarization output. This device is given by lateral mode confinement by the PBG (Photonic Band-Gap) effect by shallow etching in a partial VCSEL top mirror. The PBG area encircles a MS-region (Mode-Shaping region), which is characterized by large longitudinal mode losses. The MS-region encircles the LA-region (Light Aperture region), which is characterised by low longitudinal mode losses. The MS-region does not contribute to the lateral mode-confinement to the LA-aperture, and the lateral modes confined by the PBG area. The VCSEL is thus optimized for single fundamental mode operation.

Abstract: The invention relates to fabrication of VCSELs. It provides a method for fabricating a VCSEL that contains a micro/nano-structured mode selective lateral layer, where the micro/nano-structured layer is obtained by well controlled local etching. The invention enables control of the micro/nano-structured layer thickness with very high precision. In particular, the invention relates to a method for fabricating a VCSEL with a micro/nano-structured mode selective layer for controlling the VCSELs transverse electromagnetic modes.

Abstract: This specification discloses a VCSEL (Vertical-Cavity Surface-Emitting Laser) device with single-mode output and optionally single polarization output. This device is given by lateral mode confinement by the PBG (Photonic Band-Gap) effect by shallow etching in a partial VCSEL top mirror. The PBG area encircles a MS-region (Mode-Shaping region), which is characterized by large longitudinal mode losses. The MS-region encircles the LA-region (Light Aperture region), which is characterised by low longitudinal mode losses. The MS-region does not contribute to the lateral mode-confinement to the LA-aperture, and the lateral modes confined by the PBG area. The VCSEL is thus optimized for single fundamental mode operation.

Abstract: Illegitimate use of IP addresses is counteracted. A network (1) includes a switch (5) with ports (P1,P2,P3) to subscribers (6,6A) and a port (PN) to a core network (2) with DHCP servers (4, 4a,4b). The switch includes a database (MAC1, MAC2), port numbers (P1, P2) and VLAN identities (VLAN1, VLAN2) for the subscribers (6, 6A) and the filter has a list over trusted DHCP servers. Initially onlY DHCP messages from the subscribers are allowed. When the subscriber (6) requests (M1, M3) for an IP address it is checked that it is a DHCP message with valid subscriber values (MAC1, P1, VLAN1). A respond (M2, M4) with an allocated IP address (IP1) and lease time interval (T1) is checked to come from a trusted DHCP server. If so, a list in the filter (9) with correct information is dynamically generated (MAC1, P1, VLAN1, IP1, T1). A messsage (M5) from the subscriber (6) with false IP address is discarded by the filter. Attempts by the subscriber to use false IP address are counted and a warning signal is generated.