High-performance dense wavelength division multiplexer based on blazed grating and ion-exchanged glass waveguide technique

Data bit rate, 1dB pass band and device dimensions are the key properties of dense wavelength division multiplexer (DWDM) devices. For blazed grating based DWDM structure, analysis shows that the bit rate is limited by the pulse broadening introduced by the grating. To reduce the pulse broadening, the output fiber array channel-to-channel pitch must be reduced. By decreasing the output channel pitch, 1dB pass band can be increased and the device dimensions can be shrunk. In this paper, we propose an ion-exchanged glass waveguide chip to be inserted into the WDM device in order to reduce the output channel spacing. To fabricate the low loss fiber compatible waveguides, two-step K + -Na + and Ag + -Na + ion-exchange process using BK7 glass as the substrate has been investigated. The optimal process conditions have been found. The waveguides fabricated by this two-step process have a propagation loss of 0.3dB/cm, a coupling loss to single mode fiber of 0.4dB and a polarization dependent loss of 0.1dB for 5cm long waveguides. The design of a 48 channel DWDM with this glass waveguide chip is given.