The analytic general solutions for the complex field envelopes are derived using Weierstrass elliptic functions for two and three mode systems of differential equations coupled via quadratic χ2 type nonlinearity as well as two mode systems coupled via cubic χ3 type nonlinearity. For the first time, a compact form of the solutions is given involving simple ratios of Weierstrass sigma functions (or equivalently Jacobi theta functions). A Fourier series is also given. All possible launch states are considered. The models describe sum and difference frequency generation, polarization dynamics, parity-time dynamics and optical processing applications.Coupled mode nonlinear optical systems form a fundamental building block in optical processing functionality. Herein, we provide an extensive analytical study of both the coupled mode system for quadratic nonlinearity, found in materials such as periodically poled lithium niobate (PPLN) crystals and commonly referred to as χ 2 in optics, as well as the coupled mode system for cubic nonlinearity commonly referred to as χ 3 and typically found in silica waveguides such as optical fibers. The functionality enabled by the quadratic nonlinearity includes, but is not limited to, sum and difference frequency generation [1,2], modulation format conversion [3], optical logic [4,5], and all-optical switching [6,7,8,9]. Respectively, the cubic nonlinear system in optics can describe nonlinear polarization mode dynamics; which include instabilities [10] and has enabled such functionality as the optical Kerr shutter [11,12] and all-optical regeneration [13,14], adjacent waveguides coupled via evanescent optical fields; which are utilized in all-optical switching and optical logic [15], and most recently, nonlocal non-Hermitian parity-time (PT) symmetric coupled mode systems; which may provide a test bed within optics for theoretical physics and possibly enable novel unique optical properties such as non-reciprocity between modes and power threshold behaviour (see [16] and references therein). Outside of optics, the coupled mode equations with cubic nonlinearity also describe Bose-Einstein condensates (BECs) in atomic physics [17].The equations describing light interactions in a dielectric with quadratic or cubic nonlinearity were first derived by Armstrong et. al. in 1962 [1]. Therein, the amplitudes of two or three mixing frequencies were solved for in terms of Jacobi elliptic functions. In a Hamiltonian analysis, bifurcations and instabilities were examined in the two mode quadratic nonlinear system in [18] and the phase of the fundamental mode was solved for as an elliptic integral of the third kind in [6] under the special condition that the second mode (or second harmonic) was zero at input. It was proposed therein that the intensity dependent refractive index could be used to induce phase shifts in a Mach-Zehnder waveguide to produce an all-optical switch. A similar technique was explored in a 3 mode case in [7] where in addition to optical switching, wavelength demultiplexing a...