The Letter reports the modelling, realisation and first experimental data of improved tunable MQW based interferometric Y lasers. A new simplified tuning current control scheme featuring single control current is obtained from the asymmetrical Y configuration. Theory is confirmed by demonstration of tuning using only one current up to 8 nm which represents no limit. The Mach-Zehnder filter function of this device can be flexibly designed for specific WDM applications, e.g. the number and spacing of addressable channels.