We suggest a generalized Lax pair on a Hermitian symmetric space to generate a new coupled higher-order nonlinear Schrödinger equation of a dual type which contains both bright and dark soliton equations depending on parameters in the Lax pair. Through the generalized ways of reduction and the scaling transformation for the coupled higher-order nonlinear Schrödinger equation, two integrable types of higher-order dark soliton equations and their extensions to vector equations are newly derived in addition to the corresponding equations of the known higher-order bright solitons. Analytical discussion on a general scalar solution of the higherorder dark soliton equation is then made in detail. Since the first observation of a solitary wave in a canal almost 170 years ago, the solitary wave phenomena have been reported in many fields of sciences. Especially the soliton in an optical fiber, which was first proposed in a nonlinear Schrödinger equation (NSE) in early 1970s [1], [2], has motivated many researchers to make use of it in the optical communication of the next generation. After a huge amount of study for the practical applications as well as for the academic interest, several soliton field experiments of 10 Gbps ∼ 40 Gbps communications have been carried out recently in Japan, USA, and Europe [3], respectively. For a higher rate transmission of pulses, the wavelength division multiplexing [4] could be also taken into account to conduct the soliton transmission experiment of 1 Tbps level in a laboratory [5].In the ultrafast optical soliton system where a pulse is in general shorter than T 0 ≤ 100 fs [4], higher-order effects such as the third-order dispersion [6], the selfsteepening [7], and the self-frequency shift [8] need to be considered for the propagation of femtosecond pulses in a monomode optical fiber. Regarding the Hirota [9] and the Sasa-Satsuma [10] equations which are known to be the only two integrable types of the higher-order NSEs, the Painlevé integrability property [11], [12], an exact N -soliton solution [13], and solitary wave and shock solutions in the generalized phase function have been found [14]. Also for the description of the multimode transmission, it is necessary to accommodate degrees of freedom in cross-couplings between different modes of pulses in a vector NSE [15], [16]. Remarkably the vector solitons of polarization-locked states, which have Jongbae Kim 9