Abstract: A method and apparatus for monitoring an optical network being equipped with WDM equipment able to transmit a plurality of data channels at different wavelengths. From the said optical network a part of its optical signal power is coupled out and a specific statistical function of interest is determined which characterizes the said plurality of data channels. The parameters of said determined function of interest are processed in a predetermined mathematical model having a finite number of parameters and from said model information is derived on individual channels. Data representing the said information are produced.

Abstract: A method for manufacturing branching-off or intersecting channel-shaped waveguides on or in a substrate, which substrate encloses a light-guiding layer, and on which substrate there is applied an auxiliary-mask layer having a thickness t, the method comprising steps of:applying a first mask pattern of a first mask material in a first mask position on the auxiliary-mask layer, the first mask pattern including a subpattern for defining a first channel-shaped waveguide;etching portions of the auxiliary-mask layer not covered by the first mask pattern using first etchants, the auxiliary-mask material being etched over a first etching depth d which is less than the thickness t;removing the first mask material of the first mask pattern;applying a second mask pattern of a second mask material in a second mask position which overlaps the position of the auxiliary-mask pattern at least in part, the second mask pattern including a subpattern for defining a second channel-shaped waveguide which makes an acute angle with

Abstract: In an optical packet-switched network provided with one or more nodes (1), a transmitter (6, 17) transmits polarized packet signals (P) over optical connections (4, 5). A polarized packet signal comprises an address signal (A.sub.1) and a data signal (I.sub.0), which are generated by the transmitter with different, preferably mutually orthogonal, polarization states (;, .cndot.). In a node (1), the address signal (A.sub.1) from a packet signal (or from a power portion (P1) thereof), is separated from the data signal (I.sub.0), in a polarization beam splitter (9). From the separated address signals, a control unit (11) derives control signals by means of which an optical switch (7) is switched for further routing of the packet signals (or of the remaining power sections (P.sub.2) thereof). In a second embodiment, polarized packet signals are switched through after they have been provided with an altered address signal in a polarization beam combiner.

Abstract: A passive optical-connection network having a protection configuration consists of at least two subnetworks (1, 2), each comprising an access node (1.1, 2.1), a feed network (1.2, 2.2), and a tree-shapedly branched access network (1.3, 2.3). According to this protection configuration there is coupled an end (1.7, 2.7) of a feed network (1, 2), both over a first set (s1) of switches by way of operational connections (1.22 and 2.22) to access ports (1.14 and 2.14) of the access network of the own subnetwork, and over a second set (s2) of switches by way of protection connections (1.23 and 2.23) to corresponding access ports (2.14 and 1.14) of the access network of another subnetwork. The advantage is that corresponding parts of neighbouring similar subnetworks may be used multiply in failure situations without duplicating costly network parts.

Abstract: A low-loss optical 1.times.2 branching element comprises a symmetrical coupler (C.sub.s) with a symmetrical power distribution (1/2/1/2) and an asymmetric coupler (C.sub.a)with an asymmetric power distribution ({(1/2-x)/(1/2+x)}). Outputs (c,d) of the symmetrical coupler are coupled to inputs (e,f) of the asymmetric coupler, so that an MZ interferometer with two branches (t.sub.1, t.sub.2) is formed between the two couplers. The branches incorporate, preferably identical, optical non-linear elements (NL1, NL2), while moreover the branches exhibit an additional difference in linear optical path length (.DELTA.L) that depends on the type of couplers selected. In one signal direction (arrow D) the branching element acts as a 3 dB splitter. The elements (NL1, NL2) and the coupler (C.sub.a) have been dimensioned so as to result in a loss <<3 dB for a given signal power in the other signal direction (arrow U).

Abstract: A low-loss optical 1.times.2 branching element comprises a symmetrical Y junction (4) with identical branches (4.1, 4.2) and an asymmetric Y junction (5) with different branches (5.1, 5.2). The Y junctions are coupled by means of a common trunk (6) in which two modes that are of unequal mode order can propagate. Located centrally in and/or near the trunk are optically non-linear partial areas (7, 7a, 7b). The non-linear partial areas (7 and/or 7a, 7b) and the asymmetric Y junction (5) are dimensioned so that, for a given signal power, in one signal direction (arrow D) the branching element acts as a 3 dB splitter, whereas in the other signal direction (arrow U) the loss is <<3 dB.

Abstract: An optical coupling device for a node in a self-healing optical network, wherein the number of switching elements is reduced by using a novel type of optical 2.times.2-switch. The switch has two switching states: (i) a bar state (ss1) in which a first and a second main port are optically coupled through to a first and a second secondary port, respectively; and (ii) a half-cross state (ss2) in which the main ports are coupled through to one another and in which the secondary ports are not involved in any through-coupling. An integrated design of the switch is based on two asymmetric Y-junctions coupled to one another via a common side branch in which electrodes are active in order to vary the propagation constant. Accordingly, a compact, integrated version of the optical coupling device with only two switching elements can be achieved.

Abstract: A polarisation-independent optical device for influencing the phase of an optical signal includes, in a light conductor (11), two identical adjustable phase shifters (14, 15), between which there is placed a polarisation converter (16). Optical signal components (I) entering at the input (12) of the light conductor as TE and TM polarisation modes, leave the light conductor at an output (13) as TM and TE polarisation modes having the same phase differences with respect to the signal components at the input. By way of simultaneous control of the phase shifters (14, 15) having a same modulation voltage V, there is obtained a polarisation-independent phase modulator. By including such a phase modulator in a branch of an MZ interferometer and placing, in the other branch, an identical polarisation converter, there may be realised a polarisation-independent switch or an intensity modulator.

Abstract: An integrated optical polarisation splitter comprises a first waveguiding section (A) with a first guide (21), a second waveguiding section (C) with a second and a third optically decoupled and physically separated guides (24, and 25 or 28) and an intermediary section (B) for a coupling between the first and the second section. The intermediary section (B) comprises a first monomodal waveguide (22) and a second bimodal waveguide (23), which are optically coupled over a length L. The bimodal waveguide (23) has a propagation constant for the first-order guided mode of one polarisation (TE or TM), which is equal to the propagation constant for the zero-order guided mode of said polarisation (TE or TM) of the monomodal waveguide (22). The two coupled waveguides have different propagation constants for the remaining guided modes.

Abstract: An optical wavelength demultiplexer comprises a monomodal incoming waveguide (1) for an incoming optical signal (S(.lambda..sub.1, .lambda..sub.2, .lambda..sub.3, .lambda..sub.4)) being propagated in fundamental guided modes having different polarisations (TE and TM), a conversion device (22) for converting the fundamental modes of one of the polarisations in first-order modes of the other polarisation, a divergence area (23) in which after conversion the incoming signal enters and diverges, a phased array (3) of curved monomodal waveguides provided with an entrance plane (7) and an exit plane (S), for receiving and further guiding the diverging optical signals, a convergence area (32) in which optical signals exiting at the exit plane (8) converge into signal beams (S(.lambda..sub.i)) converging into separate wavelength-dependent focuses (F.sub.i), and exiting bimodal waveguides (33(i)) joining to said focuses (Fi), thereby providing polarisation independent operation.