Sen, who held a 3-1 head to head record against Popov, defeated the Frenchman 21-9, 21-15 in just 36 minutes to make it to the next round of the Super 750 event. He is most likely to face Vittinghus of Denmark in the pre-quarters.
Meanwhile, Olympic hopeful Kidambi Srikanth, who had claimed the Denmark title three years back, will begin his tournament campaign on Wednesday against world number 52 Toby Penty of England.
Ajay Jayaram will take on local favourite and world no 3 Anders Antonsen in the opening round and Subhankar Dey will compete against Canada's Jason Anthony Ho-Shue in their respective first round encounters on Wednesday.
The Denmark Open has marked the resumption of the BWF calendar which has been on a halt since March following the outbreak of novel coronavirus.
The Badminton World Federation (BWF) had earlier intended the Thomas Cup and Uber Cup team events to mark the restart of the badminton calendar, but the tournaments were cancelled after several countries pulled out due to safety concerns arising out of the Covid-19 pandemic. The BWF also cancelled the Denmark Masters, which was set to start two days after the end of the Denmark Open.