Puppies being separated from their moms too early in life and then put in cages could very easily develop feelings of anxiety and stress later on in life. At best, 10% of puppies will suffer some separation anxiety regardless of their nurturing because of their natural instincts to want to be part of a pack. The irony of it is, that this is the very reason many dogs end up in shelters. And of course, that only reinforces his fears. Most dogs, unless there is a traumatic experience somewhere along the way, will learn to stay alone during the day after a couple weeks.
But think of it from your dog's perspective. Dogs are pack animals and Poodle's particularly, are very social animals. They need you. You are the most important thing in his life. But you must teach your pup to . The earlier you start getting your pup used to this fact, the easier it will be, for both of you.
Start by being sure to give your pup plenty of exercise when you are together. Give little or no attention to your pup when preparing to leave the house. Ignore him for 10 minutes and then slip out the with no fuss. Same thing when you arrive home. Just go about your business for about 10 minutes, ignoring your pup. When he is calm, you can initiate some contact. You don't want him to believe that his behavior (barking, whining etc.) has contributed to bringing you back home.
If you have to, begin with short stays in his crate without you. Provide plenty of . Leave engaging toys that will keep his attention, like Kongs filled with wholesome, yummy treats. You can also leave the TV or radio if you are accustomed to having it on while you are home.
Be the "Alpha Dog" in your relationship. It is more acceptable for the alpha to leave than one of "subjects". If your pup views himself as Alpha, he will worry about your absence as he views you as his responsibility. Not only will you provide security by establishing yourself as Alpha but your dog will respect and trust you to return if he knows you are in charge.