This paper presents an overview of integrated optics routing and coupling devices based on multimode interference. The underlying self-imaging principle in multimode waveguides is described using a guided mode propagation analysis. Special issues concerning the design and operation of multimode interference devices are discussed, followed by a survey of reported applications. It is shown that multimode interference couplers offer superior performance, excellent tolerance to polarization and wavelength variations, and relaxed fabrication requirements when compared to alternatives such as directional couplers, adiabatic X- or Y-junctions, and diffractive star couplers. >

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Optical multi-mode interference devices based on self-imaging: principles and applications

Integration of the whole mode-locked laser onto a single piece of semiconductor offers a number of advantages, including total elimination of optical alignment processes, improved mechanical stability, and the generation of short optical pulses at much higher repetition frequencies. Semiconductor laser processing technologies were used to implement the colliding-pulse mode-locking (CPM) scheme, which is known to effectively shorten the pulses and increase stability, on a miniature monolithic semiconductor cavity. The principles of and recent progress in monolithic CPM quantum-well lasers are reviewed. >

Monolithic colliding-pulse mode-locked quantum well lasers

In this paper, we develop an iterative solution to the coupled Gel'Fand-Levitan-Marchenko integral equations. It will be proved that this new technique outstands other methods such as the exact GLM solution or the Fourier method. As one of its many applications, the synthesis of fiber gratings for dispersion equalization will be tackled.

Iterative solution to the Gel'Fand-Levitan-Marchenko coupled equations and application to synthesis of fiber gratings

We describe the design and characteristics of cascaded coupler Mach-Zehnder (CMZ) channel adding/dropping filters that select every nth channel (n=2,3,4,...) from the wavelength-division-multiplexed (WDM) optical signal. Using the truncated binomial coupling weight distribution, which appears to be optimal, such filters achieve low ( >

Cascaded coupler Mach-Zehnder channel dropping filters for wavelength-division-multiplexed optical systems

Wavelength circuit characteristics are investigated systematically for a family of two-port optical wavelength circuits composed of cascaded Mach-Zehnder interferometers (MZIs) with point-symmetrical configurations. A novel design method is presented for flattening their cross-port passbands (through-port stopbands). The design principle is based on a consideration of the general relations between wavelength circuit characteristics and circuit configuration symmetries. It is shown that the role of this novel design method is complementary to that of the conventional flattening method which is used for simple wavelength-insensitive couplers (WINCs) with a single-stage MZI configuration. Various optical wavelength circuits are designed by using both the novel and conventional design principles, including fixed and tunable WINCs, a wavelength-insensitive switch (WINS), and a wavelength multi/demultiplexer with a flattened passband and stopband. Measurement results are provided for some of the designed optical circuits which were fabricated using silica-on-silicon planar lightwave circuits (PLCs).

Two-port optical wavelength circuits composed of cascaded Mach-Zehnder interferometers with point-symmetrical configurations

We have realized a novel wavelength division multiplexer/demultiplexer based on rib waveguides in GaInAsP/InP. The device is a strongly asymmetric codirectional coupler with periodic variation of the coupling constant and has sinc2‐type characteristics. Our devices have center wavelengths around 1.3 μm, filter half‐widths 10–15 nm, and far end isolation down to −17 dB. The structure is suited for integration into optoelectronic integrated circuits for applications in bidirectional optical communication systems.

Meander coupler, a novel wavelength division multiplexer/demultiplexer

We discussed optical signal processing for the next generation time division multiplexed (TDM) bit rate of 160 Gbit/s. First field trials show that this technique has a promising potential for practical applications.

Enabling transmission at 160 Gbit/s

Signal performance monitoring by a new histogram method is proposed for the identification of crosstalk. It is based on a deconvolution method. An investigation into the measured histograms for signals with inband crosstalk is presented and the BER successfully evaluated.

Histogram method for identification and evaluation of crosstalk

An experimental and theoretical investigation of meander‐type wavelength demultiplexers with weighted coupling is reported. Numerical simulations have been performed combining a two‐dimensional finite difference analysis and a suitably developed coupling mode method. Devices have been realized based on rib waveguides in GaInAsP/InP with filter center wavelengths around 1.3 μm. With weighted coupling the sinc2(λ)‐type transmission characteristics of standard meander couplers change and the sidelobes of the latter devices are efficiently suppressed. We further show the determination of optimum weighted coupling for wavelength filters meeting given requirements with respect to channel separation, maximum allowable crosstalk, and total device length.

Meander‐type wavelength demultiplexer with weighted coupling

It is shown that error evaluation from asynchronously sampled RZ amplitude histograms is possible for Gaussian noise irrespective of the duty cycle. Non-Gaussian perturbations such as timing jitter can be identified from the shape of the histograms.

C. M. Weinert

Papers

Meander coupler, a novel wavelength division multiplexer/demultiplexer

Enabling transmission at 160 Gbit/s

Histogram method for identification and evaluation of crosstalk

Meander‐type wavelength demultiplexer with weighted coupling

Application of asynchronous amplitude histograms for performance monitoring of RZ signals