Hibernate: one-to-one lazy loading, optional = false

I faced the problem that one-to-one lazy loading doesn't work in hibernate. I've already solved it, but still don't properly understand what happens.

My code (lazy loading doesn't work here, when I pull Person - Address is also fetched):

@Entity
public class Person{

  @Id
  @SequenceGenerator(name = "person_sequence", sequenceName = "sq_person")
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "person_sequence")
  @Column(name = "id")
  private long personID;

  @OneToOne(mappedBy="person", cascade=CascadeType.ALL, fetch = FetchType.LAZY)
  private Adress address;
  //.. getters, setters
}

@Entity
public class Address {

  @Id
  @Column(name="id", unique=true, nullable=false)
  @GeneratedValue(generator="gen")
  @GenericGenerator(name="gen", strategy="foreign", parameters=@Parameter(name="property", value="person"))
  private long personID;

  @PrimaryKeyJoinColumn
  @OneToOne
  private FileInfo person;
}

But: if I add optional=false in OneToOne relationship, lazy loading works fine!

@OneToOne(mappedBy="person", cascade=CascadeType.ALL, optional = false, fetch = FetchType.LAZY)
private Adress address;

Question/Entreaty: please, explain to me how optional=false annotation helps to achieve lazy loading.

P.S. I've read posts post1 and post2, and understand why simple OneToOne can't be lazy, but I still can't grasp optional=false magic.