We explore the implementation of a novel protocol for fiber-based high-dimensional quantum key distribution (QKD) which improves over the traditional DPS-QKD and COW protocols. The emergence of distributed-phase-reference protocols such as differential-phase shift (DPS) [1] and coherent one-way (COW) [2, 3], have had a great influence on the field of practical QKD. Naturally, this impact has lead to the proposal of related protocols [4, 5]. We here propose a novel combination of the DPS and COW protocols, which we refer to as the DPTS protocol. To explain the principle of the DPTS protocol we refer to Fig. 1 which shows a simplified setup. Alice prepares a pulse train consisting of weak coherent pulses, which are phase modulated at a frequency of half the laser repetition rate. As in the DPS protocol relative phases only assume the values {0, π}. At this point, the pulses appear in pairs, so that any single pulse has a neighbor with 0 relative phase and another neighbour with 0 or π relative phase. We denote pairs of pulses, which with certainty share the same phase as a sub-block. After phasemodulation, the pulse train is intensity modulated in a similar manner to how it is done in the COW protocol. However, in this situation each COW sequence is repeated three times as illustrated in Fig. 1. We denote a six-pulse sequence, of common COW sequence, as a block. Note that the COW sequence is therefore always the same within a block, but changes randomly across a block separation. To interpret the stream of weak coherent pulses sent by Alice, Bob employs a Mach-Zehnder interferometer with a delay, T , corresponding to twice the temporal difference between pulses. Using this setup, WCP IM PM IM D2 D1 T T φ φ t0 D1 D2 t1 t2 t3 t4 t5 φ t0 t1 BLOCK n BLOCK n+1 }