In the last few years, the growth of data traffic has increased the interest in broadband integrated optical devices. Their applications include, for example, a possibility of bidirectional fiber communications in a single fiber, which is achievable by adding the transmission capacity of two optical telecommunication windows for local area networks (LAN) and wide area networks (WAN) or by combining pump and signal wave- lengths in rare earth-doped integrated optical amplifiers. A promising technology to realize those devices is ion exchange in glass. This allows the integration of different functions on a glass substrate with efficient results and a better compatibility in fiber systems at a low cost. We propose an original broadband duplexer based on a leaky structure, which involves a nonresonant coupling and ensures a broadband spec- tral behavior. The broadband duplexer is first presented, and the focus is specially made on the improvement of the output cross talk through the suppression of parasitical back reflections. Theoretical optimization and validation by simulations follow. The spectral response of the optimized structure displays two duplexing bands of at least 200 nm in width with a total output channels’ isolation within 0.6- to 0.8-µm range, and a better than 15-dB isolation level within 1.2- to 1.4-µm range, with a maximum of 24-dB isolation at 1.31 µm